It entirely depends on the situation. If the tank's gone beyond the call of duty (grabbing adds that are going for me/DPS etc.) then I will give it to the tank but a lot of the time I'll give it to the DPS who's doing the most damage. DPS is important (my other class is BLM) and without it fights would last far too long for me to heal through. Plus they don't get a lot of commendations.