Rend's not much a dps increase if it pushes back BT/WW. If you can do it quick in between cd's, it averages out to be higher than a non-crit hs, but slightly lower than a crit hs. I think of the stance dancing as giving up a hs, which more often than not will crit, so I find its not too worth it anymore. For you it might, since you have less haste, but like you said, you're watching your fellow raiders, so probably not worth it.
Get some more haste. Your stats are at the point now where haste scales fairly decently as it is the only way to increase the number of hs's. Rage isn't a problem anyway.
And you're gear is far better than mine (I'm a 12k guy), so take what I say with a grain of salt.