Yeah, it's not a criticism of them, it's just there's a natural lifespan (without changing the format). There needs to be some element of the unknown between the two captains or it it's just running through the motions. There's no way now that David won't be aware of Lee having a special handshake he does to give an accurate blood pressure reading to everyone he meets, or whatever.
I'd place Bob and Greg Davies on a level as being obvious stand-outs, but in previous series it hasn't felt like they're absolutely towering to the extent everyone else might not bother. Especially as a I think Bob is a bit of a rich ingredient and it'd be shit to have a series packed with Bobs (he's fucking brilliant, but he also really pushes against the walls of the game, and you need most people to play it with a straighter bat). I do think this series has had especially dull guests with especially dull material. It's the first series that's felt so tired.