I just did mana tombs with my 5 x lvl 65 shamans and I just round-robin the nexus terrors + frost shocking them, they don't even get a chance to hit me.

Ohw and having fun with allies aswell, I think when you hit thunderstorm just about right you make them fly further away.

P.S. Elemental Mastery + 5xThunderstorm (instant) = kill.

-Dyna,