Avoron wrote:All it takes is something with a way to see invis (see invis/tremorsense/etc) or have any concealment for a lot of that damage to not apply.
Plus, I am pretty sure that build doesn't actually work due to this FAQ about vestigial arms.
Basically, 'no extra attacks' means 'no extra attacks'. I know the argument you made against that in that linked thread, but this FAQ does directly address that issue.....so yeah....vestigial arms are just curiosities used for things like shields and reloading guns it seems.
But beastmorph with bite/claw/claw/rake(2 claws) stills seems perfectly valid, and extremely powerful, particularly on a sneak attacking vivisectionist. Heck, that number of attacks would be strong by the standards of a full BAB character, let alone a 3/4 BAB one. Throw the rest of your build's tricks onto that, and you still have something fantastic.