Lets talk skills and see what they lack or do not lack.

Life - Needs some kind of drop aggro spell, and Banish undead should be AOE, more healing stuff.
(all other skills should not have healing in them) why even have a healer if you can heal yourself? also id like to see some kind of godly light come down and singe the hell out of something (holy light)!
Death - should work great based on the level not how low you are in hp! I dont conider death ray as a heling spell but more of a damaging spell, i can still use it with full life. (thats the hint on its a damaging spell w/ benefits.
Air - Chain lightening needs to be tamed down!
Water - should have some kind of ice shower, also somthing like earthquake but raises up spikes of ice. (slow dmg and regular damage)
Fire - should have a fire wall, or dragon fire breath type of spell.
Earth - seems to be the only magic that pretty much has it together.
Chaos - well its chaos cant tell whats wrong or not with that tree.
All weapon skills - should have more types of skills in them (usable ones)
Subterfuge - "Under Construction"
Tactics - have some skills that hurt more than help i just avoid those altogether.

thats all i can think of at the moment..ill add later.

So start it off (again i may not agree with everyone but everyone has a right to what they believe!)

 

Mobs should act like players do and attack the healers first. Allowing healers to drop aggro within the same tree negates any risk the healers might have by focusing entirely on the tree. So no.

There's already "Escape" in the light-armour tree and even THAT has issues; primarily that it serves no function in PvP what-so-ever.

Also, Life tree has plenty of "healing stuff".

Healing is practically mandatory for every character in order to be self-sustainable. Fix that first.

Completely disagree. It's about being a dark caster that uses summons to take the hits while hurting himself to deal damage. If you're a warrior hybrid, then you become someone to watch out for as you get more dangerous as the battle progresses. When it comes to flavour, this skill tree is probably the best in the game.

... they just need to make the summons more practical.

It needs reorganization. Pickpocket should be much lower tier in the tree and work on ALL humanoid characters. I don't see why I have to be a master assassin before I can try to steal stuff; being able to penetrate armour and improved critical damage before learning to steal?

And get rid of skills that are just stepping stones like "Camouflage".