I think you've covered it pretty well, but I'd like to add a couple of notes.
Heavy Generator Defence: Noises mentioned a heavy backing up the technicians on gen D. On most maps, you'll want one or two of these. It's a fun job. You get to lay down lots of heavy damage on the guys trying to have a party in your generator room. However, you need to know your map. Katabatic has three points of entry; watch your back. Temple Ruins is too vertical, don't play a heavy on gen D. Crossfire is so cramped that standing in the generator room is suicide. Arx Novena is slaughterfest. Load up and lay the pain down.
Heavy on Flag: Most often a doombringer. Be careful where you set your force fields. They'll damage incoming cappers, but you want some room to finish them off if (when?) the field doesn't do the job. Be ready to pull out the missile launcher when an enemy vehicle shows up.
Pick a role and get good at it, but be prepared to do something else. If there are three technicians and two juggernauts in the gen room already, you don't need to be there. Try something different, even if you're not very good at it yet.
Last edited by Irimar; 28th March 2012 at 04:19 PM.
Reason: I'm a really poor typist.