I have a better build for you now. It's Earth Magic, Air Magic, Energy Storage and Shadow Arts.
Elementalist/Assassin.
Shockwave [Elite]
Crystal Wave
Whirlwind
Aftershock
Death's Charge
Armor of Earth
Earth Attunement
Stoneflesh Aura
Usage
-Cast Earth Attunement then Armor of Earth for +62AL and 33 damage reduction at 16 Earth Magic.
-Find a target surrounded by multiple enemies and cast Death's Charge. Try not to be the first player to take aggro.
-Cast Shockwave then Crystal Wave (or Whirlwind then Aftershock first if there are many attacking enemies)
-After casting as many combinations of your skills as your energy allows, retreat to the back line to recharge.
-Try not to use Whirlwind unless you can follow up with Aftershock, or if the enemies around you aren't attacking. Alone it does very little damage.