I believe you are wasting DPS by allowing your boomkin to kite. My guild CCs all of them at the start (no kiting). We manage 3 crackles in P1 (ony dies just before the 3rd).
In P3, we have our holy paladin RF heal to aggro all adds and our pally tank picks up all of them off him.
No kiting means more DPS and there's no need to heal your Boomkin.