One more suggestion. If the problem is on trash, don't attack the first target that the tank targets. Quite often they will target a mob or two to get the initial agro and then switch to another mob as their main target. Make sure you target their target after the tank has been standing still and fighting for a few seconds. What I do is target the tank and press F a couple of times after the fight has started to make 100% sure that I am on the tanks target.