My current group (on 
super duper hard) is Fire/Earth Mage, Air/WITCH/Water Mage, AIR/Water Mage, Archery Scoundrel/Marksman.  Lots of stun puddles (Rain + shocking ability), Teleportation, and SUMMONLINGS!
We're all Glass Cannons.  Summonlings work well.  If you go this route, wait until level 7 to get the talent Glass Cannon.  Ensure you have potent enough summons!