The maps in this vary quite a bit in size, and thus the player count for the different gamemodes and map should do so as well. Personally I feel that 12 players on some maps in Instant Action, like Terminal, just turns into a cluster**** in which you cannot engage anyone without a big possibility of someone else coming along to finish you, or/and, your target off, and that takes away a lot of what makes Crysis 2 a superb multiplayer as a lot of the tactical gameplay becomes obsolete.
Obviously they should keep the 12 player count for the bigger maps like Pier 17 or Shipyard, but I personally feel that 8 or perhaps 10 players would suit Instant Action a lot better on some of the smaller maps. The same kind of goes for some other gamemodes, but 12 players on the smaller maps still work when there are two teams, as teamwork still rules supreme in most cases.
Basically I would like Crytek to consider lowering the playcount depending on what map we are playing on.