Eh... simple is better...
Heal as priority,
DPS/dots when the parties HP and your MP is in the green(safe enough). (i mean if no ones taking much dmg and your just standing there like a bump on a log to cast the next heal in 5min....)
ex)
Had some instances where the healer was taking a ton of hate, i watched them and they were healing me like only when my HP was say 90%
And then last night there was the AST that was dpsing so much, everytime they tossed me a heal my HP was at 20% >.>;;
Aside from harder raids when you actually have to push yourself a little and fit that definite dps in,
most dungeons give you a choice.