In our group for 8 man we keep one of the healers on the ground dodging bubbles if you watch Stormcallers head you can see when the rocket comes out.
Man thing you want to watch is Stormcallers health drives the entire fight but you want to kill Firebrand first. SO top 2 dps on Stormcaller. In our group we rock all of the defensive systems 80 60 40, on the last one at 20% we have our range flip over to storm caller but only dps Firebrand until he dies then we all flip over to Stormcaller and wipe him out.
Thats been our strat in SM it also works in HM, we now down these guys every week.
There's also a sound associated with the bubble coming out. I don't know how to describe it, but just listen right before it comes... It goes blue spire --> yellow reticle --> blue firing sound (move now) --> blue spire.
You should be able to never get hit by them. =)