Not to mention that it's a HUGE waste of force that takes away from your potential to kill anyone. Considering how lame our burst is to begin with, losing SUSTAINED damage in order to throw a weak bubble on someone is just absurd.
I'm sorry but You have more then enough force to throw heals and bubbles with proper use of Sacrifice. And there is more then enough time to switch between targets while being attacked. If you are being focused you are going to die anyways so why not give your teammate a bubble before going. You can kite and throw bubbles at same time. Can this always be done at all times no. But Seriously it isn't that difficult. How do you think healers do it when they get attacked. Basically you are the healer if there is no healer (unless of course you don't like winning)
And If you do have a healer and hes getting trained, its your responsibility to help keep him alive. If a tank puts guard on you it's your responsibility to help keep him up.