Merc vs 2nd player

So how is it that people say that Mercs are so OP when a 2nd player wearing the same gear would be stronger and more effective?

Mercs are probably the best thing that has ever been added and build diversity during the merc league showed that. The Dory tech isn't any more powerful than just having a 2nd player in your party.

They aren't OP at all. I think some folks just see the solo crowd having fun and want to poop on the parade.