Starting at the bottom makes it, in my opinion, very difficult to accomplish. However, starting at the top allows you to rush the building on the left, or have each guy go in a different way, staying under cover, then converging on the bad guys all at once from several directions. If good teams do this, they destroy. So give it a go, but obviously be prepared to fall back on more conventional fighting.

Something else to keep in mind is that a defender titan is a fantastic one for the heavy ammo rounds. He puts up a bubble and distracts the other team (and they will be distracted) while you guys run and grab the heavy and demolish them. With this tactic Zero Point Fox employed, we didn't lose a single heavy ammo round, iirc. The distraction worked every time, even when facing a team that would normally demolish us.

Also, due to the range that most of the fighting takes place in, plus the close range nature of many of the exotics, quick revive armor pieces are more prized here IMO than in normal matches. Warlocks and Titans should probably go for theirs, while a hunter can use Symbiote or whatever he wants, since his exotics I think help a little more in this kind of a fight.

Also, because of the nature of the map, long sightlines with still hidden ways to get through to either side of the map without being seen, I do suggest The Messenger. This way you can stay scoped in to where the other team will probably be and still be aware if the assholes try to come at you with their Party Crashers. But, YMMV.