I don't have a problem with mentor in that context, and he's SUPPOSED to come off as annoying. He's also the origin of most of the comedy the series has been offering so far, which has been quite good in my opinion.
Other than that observation, not a fan of those types of characters, so...
I also have to wonder if Mob is as much of a dunce as he seems, particularly with the way he acted in the cavern. Makes me believe that he's a bit play-acting. But all told, I'm sure he's that much of a dunce as he seems, but the scenes in the cavern is making me doubt it a bit.