You can't shoot out from a Titan bubble. Anyway, I'm calling it cheesy, not a glitch, and I'm not making any judgements - I have no problem with playing cheesy. When I did it w/ my Hunter and just one other player who was a Warlock sunsinger, it seemed like it would be impossible to do w/out hiding under the stairs. Now I see that there are some good strategies that don't involve hiding in a spot where nothing can get to you.