I just have one more comment on this for the "What happens if I DPS and someone dies?"
I was reviewing some fflogs for some fight research, and came to the realization that if a Healer DPSs AND someone DIES it's STILL a net GAIN in DPS and duty clear than a zero DPS Healer.

For example if a Healer is doing 400 DPS for the whole dungeon, and a DPS is doing 800 DPS and the DPS dies, causing him to lose some DPS (50-100 DPS seems to be the operative amount over a fight per death) you're still up by 250-350 DPS. So seriously don't sweat letting people die in the beginning of learning. Unless you let a bunch of people die a bunch over a fight, it's still better.