I've got an Evoker lvl 23 on norm with lightning + fire tree. Soon I gonna start elite, with an evoker..
Give me your option.. Lighting tree I gonna take for 80%.. It's a great AoE tree, you can cast it and it attacks from itselves, however its a great tree^^
But as second tree?
Fire tree:

Firestorm: Great skill. Huge dmg, low range

Flameshards: Good range, good dmg too imo.

Hellfire: Havn't tried yet, but its good to ignite i think?^^
Spectal tree:( no experience with this tree)

Spectal Bolt: I don't know if its a good skill..but a must to skill to have Spectal Lash^^

Spectal Lash: Huge range (!) on higher level's, and in combinate with Spectal Lash Mastery, it should even be nice to kill in mass and distance

Spectal Lash Masters: Kill enemy's with Spectal Lash, and they explode + dmg and phase nearby enemys.
Venom Spirit:( no experience with this tree)

Venomous Spirit: Yes.. nice range, good dmg.. but easy to avoid on higher range.. don't have experience with this tree..

Venom Armor: On higher level + Skilllevel it can have 200-300 to armors for ~40-50 seconds.. sounds good, doesnt it?

Swarm: Yes.. I've heard its like Tempest.. but, which is bether? Since Lightning tree also give's Lightning Field

great AoE skill and huge range.
Lightning Tree:

Lightning Field: On lvl 3+ it's a good range. Damage's every1 who's in the field, and nice range. lovely skill imo.
Tempest: Cast it, and it attacks from itselves. I like it^^
Arc Legio: Dunno. Attacks all enemies actually in range ( not behind you or so tho..)
Or maybe just another tree? XX+XX.. not lightning + XX??
And the Bone tree.. I've heard its not fantastic, or not as good as the others are..
If you vote, please give me a comment, or tell me your experience with another tree's and the skills. Which are good, which are bad..
Regards, ;D