General's might does a tank buster every few seconds, even if you go into tank stance for the whole period the extra mitigation probably won't buy your healers much time to dps. Even in full defiance you can only IB 1 out of 2-3 tank busters, so I don't think your healers' dps would be able to outweigh the personal dps you gain from stance dancing.

As for your example with 4 blms, that's not a fair comparison. You're comparing a party carrying 1 bad pld vs a party carrying 4 bad blms.