Have Chain lightning continue to jump after the 3rd/last target, jumping to a new target (in range) every 1 second (for the amount of dmg it would do to the 3rd target, can crit). Call it Lightning Charge or w/e and make it a talent in elemental (deep). Lasts until cancelled (all enemies dead or spread too much, can have multiple charges jumping around.

I quite liked that magma shield idea though as well, more dmg dealt if you get hit lol. Though not the consuming the magma totem, would cost a huge amount of mana and if you don't get hit would be a waste.