is this something I'm doing wrong or a missing feature in shuriken?

texture sheet animation is fine on billboard but when I try on a mesh it stops working

I think the texture sheet animation property modifies the UVs of the particles themselves. Dunno if it'll do anything for your mesh :/

You should be able to script the offsets of your material's textures, though?

I think you have to make your own material.

try to manipulate with them in vertex shader, I'm no shader guy but it should work