We struggle on 10m heroic madness and with 6 toons.

561 blood dk, four 525+ bm hunters (me)
one 566 bm hunter and one 540 WW monk (my wife)
We pump out around 1.4 million rdps, but fall short on madness due to the huge amount of raid damage that goes out.

You'll want a dedicated tank for spine for ad control, and a couple more dps at the least for raid timers. I would say try it, and if you can't burn down hagara before she does her first lightning phase you'll need more dps.