Small apologies for the formatting and wall of text...
I am not addressing destinies yet, I mainly wanted to touch the classes themselves since destinies can be a layer on top, adding customization to your already twerked out build.

Artificer
~As a class - Artificer, decent class, needs pet and melee options as well as dc boosts. Needs a pet tree.
~~Enhancement tree: Arcnotechnician - Boost the spellpower options. Give 1.5 - 2 per point in the tree. For each core, add +1 crit chance in addition to the line. Perhaps the last 3 cores, since this would push the class as the main class. For the capstone, the boosting to items is very tempting. However it should act like the item is in your spell arsenal and be affectable by other boosts (other dc boosting gear, etc). Or allow them to use metamagics at a greater consumption (dmg boosts use 3 charges per cast, all others use 2; stackable). Also the stat boost should be +4 and the spellcraft should be class level (so +20).
~~Enhancement tree: Battle Engineer - A lot is needed here. Offer martial proefficiency, and maybe some runearm discharge procs on melee attacks. Like proc burst your runearm charges on vorpals. Also various boosts to melee should be possible. like sla prr boosts, dodge boosts, perhaps more twf and thf options (doublestrike, offhand, glancing blows), and in the core abilities maybe offer some as well. So deep delving into this tree can offer some comparable melee like tempest, or thf glancing fun. Also there is little in regards to spellpower. I think points in this tree should offer spellpower as well. Perhaps 1/per points spent in tree, leaving arcnotechnician still ahead in spellpower, but enough to where delving into both trees is useful (like the design seems to be so far). Also a runearm as shielf enhancement is needed. Also I saw nothing for the pet here. This tree should have significant pet options. Like runearm discharge through pet, boosts to the pet, and synergies from the pet to host, similar to the Arcnotechnician does. The capstone needs significant boosting. +4 to stat, threat range increase by 1 or 2, increase the attachment enhancements by .5 (From all sources), in addition to the spellpower enhancements. This also should boost stablecharging past 3, to allow the full charge on the runearm.


Barbarian
~As a class - Barbarian, it is pretty melee tough, but not enough. Needs some tweaks to make each tree shine and focused.
~~Enhancement tree: Frenzied Berserker - looks like to be more hits and damage, but feedback pain. Needs boosts to hp more. Remove str while raging boost to add doublestrike boost while raging; in the cores. Capstone needs: set cooldown to 1 minute, increase threat as well with each stack, remove melee attack penalty, set h loss to 1 per stack (essentially alowing the barb to be in this fury for a long time).
~~Enhancement tree: Occult Slayer - this is for twf barbs. Needs less dr and more dodge (swap passive core dr to +1 dodge). remove rage duration boosts and add a while raging boost to bond; gain 2 instead of 1. Capstone needs: Boost force ward by 5% or add a stacking system where the ward increases as you save, until it hits 100%, then bursts an aoe heal or damage.
~~Enhancement tree: Ravager - the rager. Needs all the rage buffs into this tree. Str, con, duration, additional rages. Tie them to the cores as +1 use, str, con, dr, +10% longer. Capstone needs to proc free rages on crits/vorpals, or refill rages.

Bard
~As a class - Needs a lot of work. Until the third pre comes out (hopefully a dc CCer), the two trees need to offer focus and competitive power.
~~Enhancement tree: Spell Singer - Obviously the caster tree. Needs more song inspired dc, samage, crit chance, reduction costs (sing to empower), sla's (sonic spells), stronger healing through song, and until the third bard tree is revealed, caster song buffs added to typical melee buffs. Capstone needs add a buff to fascinate that attempts a slay sla (the other cores get their respective slay), but the slay effect increases fasinates cooldown to 30 seconds.
~~Enhancement tree: War Chanter - this is the melee tree. Skaldic rage needs to stack on top of rage, different bonus. Add +2/-2, no fatigue. Each core should add +1 to the str component of it. Spirit should also add +1 to hit. All the self buffs should passivly add half to its equal tier (lvl 1, 6, 12, 18, 20) song. So this way bards get a buff, and their songs offer more melee utility. The armorer and weapon group should be added to the core (armorer at core 1, without the failure boost, weapon group to core 2), have tier 5 have a penalty removal for their spell failure as well as adding a blur effect to their song (or enchant armor), and weapon groups slot should be replaced with +2 critical threat (and buff their songs to offer +1) Capstone: double the stat and hp bonus. Courage should add to hit, and a song proc of sonic defense (1d6 sonig damage when hit). Inspire heroics should last 30 seconds, boostable by enhancements.

Cleric
~As a class - pretty solid. Some minor tweaks boosting their core playstyles.
~~Enhancement tree: Divine Disciple - Each core ability should add 5 to light/dark spellpower. There should be dc boosters in the core abilities as well. +1 in each of the last 3. The tier 5 empowerment should do 1/2/3 for the spell level and cost 1 per. Capstone: Double stat bonus, spellpower, and 50 spellpoints. Also should have a threat reduction toggle.
~~Enhancement tree: Radient Servant - Solid healing tree. Perhaps more crit spell chance (add one to tier 1 and one to tier 5). The capstone should have double stat bonus.
~~Enhancement tree: Warpriest - The ac boost per core should be 3, smite should increase hate, sacred touch should double its prr bonus, and proc on ameleorating strike as a tier 5, 2 ap bonus. The capstone should double the stat bonus and add 10 prr.

Druid
~As a class - Solid, needs a pet friendly tree. Nothing in the trees boost pets, so maybe that until the third pre is there. Needs a pet tree.
~~Enhancement tree: Natures Warrior - The melee class. The tree is fairly strong, so nothing really is needed, save doubling the stat boost on the capstone.
~~Enhancement tree: Seasons Herald - The caster class. Pretty solid. The capstone is strong, needs double stat and maybe double dc.

Favored Soul
~As a class - Pretty solid class. Decent trees as well. Needs a tree that favors healing, similar to radiant servant.
~~Enhancement tree: Angel of Vengence - spell pen needs tiers (1/2/3), crown should grant <alignment> to targets attacks. Vengeful magic should do +1% crit @100% health, +1 DC and crit at 75%, +1 dc and crit again at 50%, and +50% crit chance (yes chance) at 25% or lower. The capstone needs double stat and offer different slas for blades, hunter, and deathless; to be in line with the offensive powers of the first three.
~~Enhancement tree: Warpriest - The ac boost per core should be 3, smite should increase hate, sacred touch should double its prr bonus, and proc on ameleorating strike as a tier 5, 2 ap bonus. The capstone should double the stat bonus and add 10 prr.

Fighter
~As a class - fairly solid after the first enhancement pass. But needs some tweaks. Perhaps a 3rd tree for partner tacticals.
~~Enhancement tree: Kensai - Dodge cap raises should be for all armor types. The tactical dc boosts should be +1 per higher. The weapon group specializations should also increase AC by 1 per specialization tier, or +2 per. Like warpriest, I think this tree needs core boosting. +3 ac and 5 prr per core. The capstone should be double stat and upgrade one cut to improved vorpal.
~~Enhancement tree: Stalwart Defender - Similar to warpriest, this needs some core boosting. +2 ac per core and +3 prr per core. Add a tier 5 ability to consider offhand weapon as a shield (if two weapon defense feat doesn't get modified to do so). Capstone needs double stat bonus and double dc boosting. The healing should be stronger, like 5-20 per hit.

Monk
~As a class - Very strong class, needs minor tweaking on its capstones and ninja spy needs more bluff abilities.
~~Enhancement tree: Henshin Mystic - A solid tree, the capstone should have double stat bonus, but everything else is good.
~~Enhancement tree: Ninja Spy - rogue based melee, Diversion and shadow double should throw a bluff against the enemy so you can sneak attack longer. The capstone needs double stat.
~~Enhancement tree: Shintao - healing based melee Solid as well, capstone needs double stat.

Paladin
~As a class - Needs a spell/sla tree that adds more spell utility. They could all use some deity tie-ins.
~~Enhancement tree: Knight of the Chalice - smiter. Maybe some defensive/heals from smite uses or turn uses. Needs turn and smite regen in the cores as well as lay on hands. Capstone needs double stat and a boosted smite attack.
~~Enhancement tree: Sacred Defender - similar to stalwart. Needs loh regen, smite regen, and similar core boosts like stalwart like mentioned above. Perhaps also the off hand weapon as shield ability as well. Capstone needs double stat, a threat gen increase, and a shield boost (enhancement boost up to +5).

Ranger
~As a class - Pretty solid class. Needs some moderate tweaks to help make them more flexible and viable. Doesn't offer much for using wild empathy to take control and make enemies pets.
~~Enhancement tree: Arcane Archer - arrow effects. The top tier elemental abilities should be aoe crit procs. Arcane archer enhancement should stack (push to paragon and epic), true strike should have a crit multiplier and threat range boost for higher ranks. The capstone should have double stat and add to your arrow DC's by +5-15 (I am guessing +5 per enhancement rank).
~~Enhancement tree: Deep Wood Sniper - favored enemy ranged power. Choosing melee based options should add to +1 or 2 to dodge each. The hit and damage bonus from favored enemy abilities should be double. The capstone should offer double stat, +2 sneak attack die, the range boosts, and also boost aimed shot to have +1 threat range, and double the hunters mercy and head shot hp amounts they deal.
~~Enhancement tree: Tempest - twf. Much like warpriest and the defensive melee trees, this one's core should add to AC, 2-3 each core. Improved defense should be double, whirling blades should also add +1 to dodge and cap per blades picked, and also be a requirement for dance of death, and dance of death should have a +1 threat range passive. The capstone should have double stat and remove the ac penalty from the growing storm and increase its stacks to 25.


Rogue
~As a class - Pretty solid, but not much combat defenses in the core tree. Mainly dc boosting needed.
~~Enhancement tree: Assassin - kill based. Sneak training should reduce threat by 2-5% each tier and be a requirement for knife specialization. More weapons should be added to the cores and spcialization (maybe all light weapons+some light exotics). The capstone should double stat and have a level drain clickie.
~~Enhancement tree: Mehcanic - ranged rogue build. Needs some more ranged sneak and pbs extensions, like 5 every core. Has some utility with building traps. Remove the half level dc and make it full level. The capstone should be double stat, boost improved traps dc by 4 (making it +5 to the dc's). and modify rapid fire to also include +1 threat range for all ranged attacks.
~~Enhancement tree: Theif Acrobat - staff builds! Pretty solid. Dc's should use full rogue level instead of half. Tumbler should increase dodge by 2, and cartwheel charge should as well. Capstone should have double stat and increase tactical dcs by 3-5.


Sorcerer
~As a class - Strong caster class, needs a small amount of defensive boosting.
~~Enhancement tree: Air Savant - Needs dc boosting for your element in the cores. Double the dodge bonus in the tree (not capstone). Capstone needs double stat.
~~Enhancement tree: Earth Savant - Needs dc boosting for your element in the cores. Earthen armor should add 5/10 ac instead of 1/2. Capstone needs double stat.
~~Enhancement tree: Fire Savant - Needs dc boosting for your element in the cores. Capstone needs double stat and modify fire guard to be fireshield at the same time (fire).
~~Enhancement tree: Water Savant - Needs dc boosting for your element in the cores. Capstone needs double stat. Should add an ice guard with ice version of fireshield to it.
~~Enhancement tree: Eldritch Knight - The cores should add +2 ac per core, the armor proficiencies should each add +2 dodge, and the capstone should have double stat, +1 threat range and multiplier as well.


Wizard
~As a class - Fairly solid. minor defensive boosts.
~~Enhancement tree: Arcane Master - Flexible casting. The capstone should add double stat, 10 spellcraft, and +2 to spell crit chance.
~~Enhancement tree: Eldritch Knight - The cores should add +2 ac per core, the armor proficiencies should each add +2 dodge, and the capstone should have double stat, +1 threat range and multiplier as well.
~~Enhancement tree: Pale Master - Fairly solid tree. Tier 5 shroud bonus for stats should eb double and increase necro dc's by 1. Capstone should have double stat and add +2 to necro dc's.


As you can see, I went all Oprah on this!