Seriously helpful ability buff, it really helps quite a lot if your character has problems staying alive... It increases your damage output significantly while it is active too. Elemental Boon also will apply to your allies so the bonuses are passed along to your group.
However this ability has one major drawback, it has a 15 second duration and a 30 second cooldown so at best you can only have it active 50% of the time, you cannot improve the duration or cooldown with ranks either, its also a pain to remember to cast it every 30 seconds...
Tier I Bonus:
Gains resistance to slowing and immobilization effects
Tier II Bonus:
Gains mana recharge
Tier III Bonus:
Faster cast and less mana