I must admit, I'm one of those people who seldom use cooldowns on bosses and saves them all for those unexpected incidents where everything suddenly goes south and I need to keep myself going for a while. That, and saving them for the next group pulls.

In any case, I always appreciate when healers help out with the dps. At first I thought that maybe your tank was just taking it out on you for pulling hate at the start by being "aggressive" and not giving him a chance to establish enmity, but considering how he never seemed to use Flash anywhere else, I guess not. Getting people who queue together can sometimes be really annoying as the other person will likely assume the "I am his friend so I will defend him by default because he is definitely right" position and they only reinforce each other into a position where they cannot possibly fathom that they just might be wrong.

Anyways, by the sounds of it I think you do this already, but all I would say is that if a tank is struggling to keep enmity for any reason whatsoever then don't make it even more difficult for them by dps'ing, but otherwise help out by all means. I'm sure most people welcome it and you are just getting a bit unlucky at the moment.