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!