mid-40k sustain looks pretty fine to me. better question is why are you eating all those epicenters dude? stunning them makes the fight so much easier. your raid is pulling almost 160k hps. our kill it was about 115k.
Well we had Rogue trying to take those fists, somehow he was missing randomly anyway those. Then i told we could maybe have other tank taking fists. it was pretty messy also.
it took us a couple practice pulls doing epicenter wep first to get it down, what we ended up doing was having the whole raid stack in one direction of the boss so the fists went through in a predictable direction. we then had the mage stay still while the rest of the raid moved. tank copies mage, mage gets hit with ice barrier up for half his life, mage blinks out, tank gets fists of thunder.
you just have to be careful not to copy too early or it will expire. its worth it doing a few practice pulls with epicenter first to get the hang of it. it makes the fist weapon phase almost mana positive.
anyway, concerning throughput: as far as i understand mistweaver monks are putting out crazy numbers so i wouldn't be too discouraged on that front. your sustain looks fine and you bring slt, htt, and mtt to the table.