I have been over all down right unimpressed/disappointed by the 20 levels in a class required capstones. By and large with the exception of monk, barbarian and FVS, level 19 and 20 are dead levels with little benefit that would not be great out weighted by two levels in a complimentary class or one in two of them.
If anything the enhancement pass will further enhance the value of multi-classing 1-5 levels in another class as it will open a host of other abilities that were not present in a pure character. The 20 level capstones need to be adjusted to be in line with the with the level of power a character must give up in order to take a sole class into epic levels.
The Capstones needs to be far and away the best enhancement on the entire tree and should make the character truly outstanding in their focused field.
It is difficult to make suggestions on what the capstones should be as not all three trees are even close to what I had expect and the current capstones are basically imprints of the old ones. I will use my example for the cleric trees that should have been.
Diety Weapon / Melee focused
The tree should have been about increasing your dietys favored weapon, spending turn atempts to increase melee damage and significantly discount personal combat buffs. The idea being a melee battle cleric that hits hard but still has most of its mana available for healing.
The capstone would be While wielding your dietys favored weapon you have a full base attack bonus, add your wisdom bonus to melee in addition to strength and your next healing domain spell after a critical hit has empowered healing added for free.
Healing Conjuration and Abjuration
This tree should have been the healer tree. The abilities would be mostly about improving healing effectiveness, adding alternative healing methods, mostly through adding effects to the cure lines, improving efficiency to the point of empowered healing being free-ish, increasing the range and area of healing spells and improved protective buffs. The idea of this tree is to make healing fast and easy allowing either a relatively weak game player to fulfill his party role or a skilled player to micro manage a ton and use a combination of healing and crowd control to help a whole raid.
The capstone should be a positive aura stance that heals all within it, possibly with the exclusion of the cleric it is centered on, with added stacking protective buffs and periodic negative effect cleansing, side effect of turn undead triggering on the same timer as the cleansing.
Exorcist/ Holy Vengeance
This tree should be all about light, force and alignment damage. Alternative uses for turn undead, possibly to include daemons, devils and aberrations. Spell like abilities that can do respectable amounts of damage for low SP costs and strong crowd control abilities. This tree should definitely include a silence SLA that can be point in space targeted. The purpose of this tree is similar to that of the melee cleric. Give them something to do that can help the party damage wise without sapping their SP too much so that they can still heal sufficiently without just becoming a nanny.
The capstone that I would see fitting with this tree the most would be a SLA similar to meteor storm but light instead of fire damage and it would do slightly less the meteor swarm does now to most targets but would do double damage to undead, devils, daemons and aberrations. I would also give the explosion splash positive energy that heals players and damages any of those four types.
Remember these capstones are intended to be VERY strong as a balance to the sacrifice you make in dedicating yourself to a single class and a single tree. I would love to hear what other capstones people feel should be made for either already released trees, yet to be released trees and other trees that should have been.
P.S. Core abilities should be auto granted as you are already paying a cost in level and in points spent in tree, but if so capstone would need to be purchased if at exactly 40 or free if above 40.