I only "just heal" when I am being lazy.
I know I can DPS but I've made a choice that run not to do so. I'm a healer... if you're not dead then I'm doing my job. It should be at the discretion of the healer if they choose to DPS not the rest of the party. ( for example I also do not DPS while healing if i'm feeling sleepy / just woke up. I don't want anyone to die because I get tunnel vision. )
It's roulettes not AS. Also since it is roulettes if things are dieing that slowly without healer DPS then you need to look at the DPS in your party, not your healer. Yes healer DPS can make a huge difference but I know for a fact that mine does not. My DPSing is just my trying to be helpful in moving things along if the DPS are that bad.