have you ever considered mana usage?

I know sometimes im standing there "doing nothing" because it's a hard fight, everyone is (currently) full health, and I am conserving my mana for heals... not DPS, because i get low occasionally. Do you actually watch for this, or just assuming they are lazy/unskilled? Would you rather have heals, or have your healer go oom cuz she was dpsing? Tanks dont watch my mana quite a lot and start boss fights while I'm low, and i end up having to conserve.