Is it pointless to bring up poor supervision during PhD viva?
I'd suggest that the viva is possibly the worst time to do this. Almost anything you say could be interpreted as whining and trying to deflect responsibility for any shortcomings. Many things you might say would be countered in the minds of the reviewers whether expressed by them or not. 

Whether you bring it up yourself or just reply to questions or comments with complaints about your advisor or others would seem, to me at least, as unprofessional. 

If you have issues about the performance of your advisor, make it a separate issue in an appropriate venue after the degree is in hand.