Lusidious covered this a couple of posts up but to reiterate, if I am healing in a well-geared group that doesn't need a lot of healing attention, then darn right I will add to the dps or CC to make the fight a little faster. On my Operative, the Shiv attack (melee damage) also triggers my Tactical Advantage which is needed in order to burst heal, regen energy AND increase healing output. So yes, I may be stuck into the fight as long as it is safe to do so as it makes for more efficient healing.
This is not a game where the healers stand back (or sit down a la L2) and throw an odd heal up now and again. If a healer isn't constantly working in one way or another then they are slacking.
Yeah, if the tank has good aggro and has a lot of health, I throw in a sabotage charge every once in awhile with my scoundrel if I have some energy. Or if it's not going too bad, I've run behind a target and hit it with a back shot or sometimes a dirty kick. Then trigger that silly surrender thing if needed.
Though in one heroic PUG, we didn't have
a tank, just my scoundrel, a commando and two sages. Heal-o-rama, plus using the force lift and tranq to keep some enemies occupied. I ended up doing more healing since they had that annoying gas grenade that drives you out of cover, though I was still throwing some attacks in.