Is there a reason you're not dealing with debuffs properly? Even putting the stun aside, your team has no chance on green affinity, and will likely lose a lot of damage on blue due to debuffs being resisted when you have acc down.

That said, stun will usually target weak affinity first, then lead, unless someone is low enough in remaining hp for cb to think it can kill it.

Also, skullcrusher; he self-cleanses off the stun,

But Kram raises more important points ^

Well since I have gotten through nightmare without much coaching I guess now is the time to ask for help. When you say im not dealing with the debuffs properly do you mean taking care of the CB poisons or the debuffs my toons are putting out?

Self cleanses but still loses a turn, so you need him 4:3 if you want proper rotation. 

There are two critical debuffs to deal with. The stun, and on green cb, the speed down debuff. The former can be dealt with by either blocking it with block debuffs, removing it with cleanse, or eating it by having someone non critical take it (eg a dps). The latter MUST be dealt with through block debuffs or, very rarely, a perfectly tuned team and debuff removal. 

Thanks for the tip.