If you're not hitting when it looks like you are then it's probably an issue of lag not bad hitboxes. Google "Brazilian laggers".
If you wanna talk about hitbox issues, let's talk about how females are harder to hit due to smaller hitboxes. That's a bit lame if you ask me. I thought they sexes were equal eh?
Essentially, you swing at someone with really bad lag and it looks like you hit them but really it did not register. On their screen you freeze so they can hit you. ATM, lag gives an advantage to the lagger.
This could have changed with recent patches, but I've not played enough to find out.