DBSK Great for soloing bosses.
Trust me, im level 39 and i solo'd all chaos bosses, including drakath, were you have to fight him like 5 times and the last time he has like 100k health.
Necromancer is great as i have heard.
So is pyromancer, so is elemental dracomancer.
Troll spellsmith is great for PVP apparently.
Imo, just research into them