I just did it with a sentinel to draw fire, a medic to heal, and then attack the guns first with your ravager. Or go with two attackers and a medic if you feel confident. It took me a while to even realize there were separate targets to hit here. Just destroy the guns first and you'll be fine. Once you get those it's easy. This worked fine for me without anyone getting remotely close to dieing.
[Edited by bloodhunt, 12/26/2010 6:17:44 PM]
Wait. Why would I use ravager? It was much easier to use commando sentinel saboture/medic.