How, as a SCH at 60, am I supposed to heal my MT and OT while attempting DPSing in 8-man Raids when they're both wearing full strength gear and have their stats specc'd to strength?

I'm not bashing, I'm legitimately curious, because I'd like to be more useful but as soon as I swap to cleric stance they're already down to far below half health. Any tips from the good healers around here?