Well if I can handle healing and dpsing, shouldn't I be able to? I only do it if a tank is well geared, knows what he is doing, and I know the layout of the level so they don't have to wait if I go OOM.
Of course, there have been times where I was dpsing and and a dpser life dropped faster than I anticipated (standing in damage, not paying attention) and i couldnt shield, guardian spirit, etc fast enough to save him. But 99/100 of the time it makes the run go alot faster.
I set up my heals first, before I do damage, making sure people are topped off and wont go below 3/4 health before I start healing again, rinse and repeat during a pull.