I get your point, but I see it differently.
No reason to "blame" Painter either way...that said, it is Painter's job to win, and hopefully, win big (or at least when it matters most). He is charged with putting together a team that can/will do that, and then developing it accordingly so that it has the best chance to do so. He did not succeed when he had Biggie last year, and chances are, he won't succeed in doing so next year if Biggie leaves...so while "blame" might not be accurate...holding him accountable for that is certainly fair I think. PG was a glaring issue for Purdue last year...it was his job to address and alleviate that...he did not...that is fair to hold him accountable for, whether that constitutes "blaming" him or not.
I disagree that Purdue is not better with him than they are without him...I am hard pressed to believe that any team that loses a guy with his talent and skill set, especially on a team where said talent and skill set is among the best (if not the best), is better without said guy. To me at least, they won't just be different...they will not be as good either.