Actually, there are several "magic tricks" to Garrosh and if DPS is so low that you're getting a third intermission, it's probably a strategy/execution problem more than a raw-output problem (headless chickens fleeing from adds and desecrates do very little DPS and people out of position when MCed messes everyone else up). It's possible to get a third whirl, go to the third intermission and then push Garrosh down to 10% before he does another whirl, ending with 3 whirls in phase 2 and only the 2-3 more you're going to get out of phase 3. And, in fact, most kills that were done without much SoO gear were probably done this way. "You can only have two whirls OR YOU'RE GOING TO DIE" is a myth. Of course this fight gets significantly harder without DPS to overpower it, but that's not really useful advice in this context.