DMing in Citadel can be fun yet very costly.
They main thing you must follow by when in Citadel is STICK TOGETHER!!!!!
If you stick together Recons will have much harder time sneaking up on you and the wounded dont have to run and hide to find a med.
Personaly Ive had a great deal of success in the Citadel using the following classes
3 ppl-2 meds 1 assault...DUH
4 ppl-2 med 1 assault 1 Mauler
5 ppl-3 med assault mauler.
Now Unless the oposing team Heavys/Guards these class varietys will work.
If they do Heavy, youll need couple of meds and a lance.
But before switching classes Anounce it to your team or else everyone might decide to change to the same thing, resulting in slaughter =p
If your team starts losing by 10 kills or more, FALL BACK, set some clays and camp in a fairly closed area and pick ppl off until you regain lead.
Hope this Tactic helps