If your goal is doing legendary and epic elites, you're going to have to decide between melee or caster. Trying to do it all will work in legendary and epic hard but will likely just lead to frustration in elites, as you have discovered.
A caster druid can solo and do really well with most ee's but will not be as fast as some other classes at doing so. EE's that I personally struggle with are those with beholders or other anti-spellcasting elements like GOP and Terminal Delirium. You can check out some of my
EE solo videos on Ginger as a comparison and to see if the performance is similar to yours or if you are looking for higher dps, etc.
Ginger struggles with soloing LE's. LE Creeping Death took me an hour and I had to use every last spell point clicky to do so. I could not solo LE To Curse the Sky on Ginger in my regular destiny of Sentinel because a large portion of the mobs (abishai) are immune or highly resistant to a druid caster's primary damage types and there's not a whole lot that anyone can do about this. Thanks to Slarden's advice, I tried it again in other destinies. Shiradi did not make a big enough difference, but I was able to solo it in Exalted Angel, however it took a long time because I basically had to exclusively use Divine Wrath and Sunbolt and had to perpetually wait for them to come off cooldown. Taking feats that offer non-elemental damage types like Ruin, Greater Ruin and Arcane Pulse will also help with mobs like abishai.
Your feat and enhancement allocation are too divided between melee and caster and this is contributing to your feeling of being spread too thin. If you're not happy with the performance and you want to focus on the caster side of things, then drop all the Nature's Warrior and melee stuff. Get rid of Improved Crit and Augment Summoning (I love this at low levels but I trade it out in early teen levels). I use Elusive Target, but Ginger is a tank, so unless you are interested in being tanky, then this can probably be traded for something else. I understand that you like playing in all 4 forms, but a caster druid should run exclusively in elemental forms. Wolf is for melee builds and bear is for... I dunno maybe flavor lol.
I really like Energy Burst (cold) on my druids, so I will disagree with some of the others here. While it may not be as effective as a intelligence or charisma caster, it's still worth taking imo. Some caster druids invest heavily in int for bonus to spellcraft and burst dc, or like Ginger I like higher charisma for skills like intimidate.
in LE tempest spine I find that I play the role of healer, cc and tank. Ginger can stay toe-to-toe with all LE TS mobs except Sorjek, which has been really handy in keeping mobs like the assassin and the inevitable off of the rest of the party. I have found that a 67 DC Earthquake is somewhat effective in LE's (effective enough that it's worth using), but I am hoping to get my DC in the low 70's. The bar for an effective LE Earthquake DC is a lot higher than EE.
There is lots of great feedback in this thread so far and I hope it helps you get on a better path toward accomplishing your goals