Since Anderson Silva tore through the UFC MW division, people have been labeling it as weak.
This may or may not be a misconception.

I was wondering what would need to happen in order to eradicate any notion that the UFC MW division is "weak".

Basically, who needs to beat who? Henderson is an obvious target. Say for instance if someone like Cote or Marquardt beat him.....would that be enough?

What needs to happen in order to legitimize the MW division?

Good question, but i think it's simply a biased opinion because of Silva Dominating Rich Franklin who dominated the rest of mw.