There are people who are jerks to medics and get angry when they don't get healed, but I think a lot of the time it's just a lack of information on both ends. Medics aren't magic, but the hurt do not necessarily know where the medic is and may know things the medic doesn't about the situation. When I am in critical need of healing, I hit the medic button. Then I pull out my equalizer unless I know the medic is right there. I have to retreat to live and I might pass a medic who is like "DUUR EQUALIZER". Not that I mind, it tells me I passed a medic, but still. It seems to ignore the fact I am running for my life.
At the same time I'm sure any decent medic has had a soldier pounding E with the equilizer out right in front of them.
Generally though it's reasons like this that I tend not to get annoyed at what people do or my team. My expectations are always that I have to rely on my self to survive and no one is going to notice me enough to puff me or throw piss at me or heal me. People got shit going on and concerns of there own. So I hope medics understand my situation, because I understand theirs and am not going to cry if they don't feel like chasing after the soldier with the equalizer out -- heck, they probably shouldn't. If I didn't notice them, thats my fault and they should go be useful to someone else unless they feel generous enough to alert me of their presence. Only time I can ever get slightly annoyed at medics is when they get heavy tunnel vision. Especially at the start of the round where I can start rocket jumping to the point with a little juice and the Heavy will be overhealed still, LONG before getting near anyone. Even thats just a slight annoyance.
I only tend to get annoyed at catastrophic levels of incompetence.