Conor would KO Lombard fairly easily, c'mon. Lombard's arms are as long as my toes and he's not fast enough to even know where Conor is.
At WW, the only real threats I see are Rory (due to being really long and a good grappler) and Wonderboy would straight KO Conor. GSP would grapplefuck him I'd expect, although Conor could possibly get the KO. Other than those guys, nobody comes to mind who is such a huge threat to Conor at WW. I'm sure I'm missing some legit guys but I can't think of them now. Maybe Maia but I don't know if he could even get his hands on Conor before getting KO'd.
The thing about Conor is that he's very mobile, in your head, and only needs a few connects to have you wobbling. To beat him, you have to literally keep him from landing on you repeatedly and nowadays that's hard to do. Wonderboy could probably do it with his eyes closed, but who else? I know it sounds silly, but Conor's style is very hard to manage.