If you,say, CC the healer after you DPS them to about 50%, why not kill their teammate that now isn't able to be healed and probably will not get heals as self-preservation instincts apply in video games as well!
1. If you are talking about CC which does break on damage - good luck with that in a PUG.
2. If you are talking about damage friendly CC (e.g.stuns) - why not kill the healer instead of switching targets - after all, you already have him on 50% and just CCed him?
I agree, though, that common sense should dictate the target in each situation and no preset list of priority targets. Therefore, I do not understand why you have included a list yourself.