It is time to grow up and stop acting like children. Gone are the days when you could do anything you liked and knew that the healer would save the day, kiss away your booboo and make everything better. Now you have to think before you act. I do not have time to pamper your behinds. If you stand in fire I will grant you heals sufficient for you to react and move out, but nothing more. I will only help you with the things you can not avoid, not with the things you can. Your rotation is only as good as your lifespan and your life is your biggest priority. We both benefit from keeping you alive, so don't leave it all in my hands. Remember that you dying probably is a bigger set back for you than it is for me.
Don't tell me that I could've healed you because I have mana. You see, mana is alot like money. Just because I have some doesn't mean I can spend it. And it definitely doesn't mean I can spend it on anything. I have priorities too. Would you use your energy/rage/mana on any skill? No, because that would lead to bad dps. I don't use my mana on any skill because that would lead to bad healing. And you don't dps just any target, because that would most likely lead to a wipe. I don't use my skills on any target, because that too will most likely lead to a wipe. We are not so different after all. If you don't understand this I will assume you have the mental capacity of a 5 year old who complains when mommy doesn't buy him candy.
And even if I had unlimited mana, which I don't, I definitely don't have unlimited gcds. Just like you I can't throw out all my skills at once if I like to. I can use one skill each gcd, so each gcd I have to choose between you, every other guy in the party and the tank. Who do you think I should prioritize?
When you take alot of damage you can safely assume that everyone else is too, so remember that if I'm not healing you it's not because I'd rather sit around with my finger up my nose and count the dots on my walls (lost count at 2000). Believe it or not but I am as eager to succeed with the fight as you are! I dislike corpse run as much as the other guy! And if our goal is to kill the bad guy without dying ourselves, we should be able to agree that we'll all do anything in our power to attain that goal together. In your case that includes staying alive, by any means necessary, whilst also dps. In my case it means staying alive, while also keeping you alive.
You don't like to move from your dps target any more than I like to waste mana healing your ass when I don't have to. So we have to compromise. You avoid the damage you can avoid, and I'll heal the damage you can't. Deal?