24 mans aren't true 24 mans. The content is split up into 3 groups of 8 in separate parts of the dungeon. So Im assuming you will only need to worry about the dot cap for your group of 8.

There is no mechanic in this game for a true single group of 24. 8 is the maximum size for a group. Content that requires more will simply be done by 3 separate groups, 6 tanks, 6 healers, 12 DPS, in 3 groups of 2 tanks 2 healers 4 dps.

The only real question is will all of CT be one zone where the cap applies globally, or is the cap group specific or target specific. I am pretty sure it is target specific, in which case you need not worry because all 12 DPS won't be on one target.