Since the game isn’t really working at the moment, at least in the EU, here’s a fun little survey.
I’ll start and keep it short.
I’ll take the order from left to right in the class selection.
Amazon
Bow Tree
Strafe 
Passive&Magic
Decoy
Spear&Spear
Fend
Assassin
Trap Tree
Wake of Fire
Shadow Disciplines
Speed Blast
Marial Arts
Dragon Tail
Necromancer
Curses
Attract
Bone&Poison
Corpse Explosion
Summon
Raise Skeletal Mage
Barbarian
Warcry
Battlecry
Combat Masteries
Natural Resistance
Combat Skills
Frenzy
Sorceress
Cold
Glacial Spike
Lightning
Charged bolt
Fire
Hydra
Paladin
Defensive Auras
Redemption
Offensive Auras
Fanaticism
Combat Skills
Vengeance
Druid
Elemental
Molten Boulder
Shapeshift
Feral Rage
Summoning
Grizzly
What do you like most? Please only one skill per tree, even if it is difficult.