@OP
I DPS if the group makeup allows it.
If the Tank is fragile, I only cast Aero.

If the dps eat alot of attacks or I am Heal Tanking. I don't even cast Aero.

Its funny cause I've had groups where folks scream at me for not DPSing.
To DPS and it not be a waste of mp is to throw up Cleric Stance, which can be a death sentence for the Tank if something goes awry.

95% of folks who kick you for this have never leveled a Healer I bet.