First time I shot at at theatrical type venue with a DSLR although I shot at similar venues before with flash; so I know what to expect. Even that, I find this type of performance quite challenging. Especially bad when the performers wear white or similarly bright outfits. I think I would get better result if I put -0.3 EV and post process later.
Anyway, here is some samples from the new Tamron. My son is on the left.. the bugger forgot his lines.