First, I wasn't saying "Whitner is garbage" (and I don't think you thought I did). He's an OK player and he's making a lot of tackles on a team with a sieve as a defensive front. (I don't think he is very good in pass defense and that is not just a "stats in a vacuum" comment -- it is from watching him play and seeing opponents target him.)
Second, you raise good, fair points. They may go somewhat as to why the Bills had him overvalued in the draft. At OSU, he played on a defense with some excellent college players all around him. The flip side of that though is that great players make those around them great. Troy Polamalu isn't merely the recipient of Fate's good fortune. He's not just another uniform out there that happens to accidentally be in the right place at the right time by cosmic coincidences. His instincts, awareness, and knowledge of the game allow him to be a game changer, which allows other people on his defense to also make plays. The Steelers defense is utterly different with him than without him. With Whitner, the Bills have moved him around and he has missed time and some fans even say the secondary play improves when Wilson or Scott were on the field. For the Bills to get better, they need to add game changers to their roster and not just keep decent players that might make some great plays if they were surrounded by All-Pros.