I dunno...
It certainly is frustrating, but what is more frustrating is that people keep on using AoE or actually directly hitting CC'd targets. Seriously, I'm happy I have a "pull out group member from danger" ability, because if I didn't - wipes would occur way more often.
Just last night I had "fun" with a group, where tank jumped into danger without as much as a word, but that wasn't what iffed me the wrong way. Allright, he jumped in there - I knew he had a load of health and armor and he wouldn't just die like a rabid dog. Thus I shield the tank, to give me some time before needing to heal him, and look for a standalone strong target to CC. So I levitate the target, and get back to healing the tank. And what do I see about five seconds after the mark was CC'd? I see the freakin' sniper charging his "ambush" ability on the CC'd target! WHY!?
Why the heck tanks can recognise a target getting controlled in the middle of the battle, but most dps can't? Don't you look where you're shooting?
A group fights a stack of mobs and accidentally pulls another stack. Happens, right? So two hardest mobs from the new pack get controlled immediately, so that we would have less to worry about. And what comes next? RIGHT, the mercenary hits the whole pack with an AoE rocket barrage thingy. Yay, now we have more golden mobs to kill you, dear merc!
If I put a mark on target and say I'll CC it - it means I'll keep re-CC'ing it as long as needed to finish off other targets. Don't just assume that if control ran out you can start spamming that target. If the other targets are still alive - the marked one will be recontrolled asap.
Whew. Some people...