I've seen this happen before. I had a group one time in CT that kept saying the tank couldn't keep hate but their FC mate could tank better. I watched at the start of every pull they would pop all CDs and try their best to steal hate to make the guy look bad, but they wouldn't do this when their FC mate would try to MT. That being said, I don't see silly stuff like that happen that often enough to say it's a huge problem, but it happens sometimes. If it bothers you a lot, just ask to be kicked or take the hit and hopefully you don't end up with people you don't like next time.