I agree with you, Smokymtngal, that none of them could take his place. I have to say that, more often than not, I will FF through the segments done by Jason Jones and/or his wife Samantha Bee. I don't have an intense dislike for them. I just don't find them interesting, entertaining, or funny. Mandvi is pretty ok but I wouldn't probably watch a whole show hosted by him.
I think Oliver would have been the only replacement I would have watched, as he did such a stellar job when Jon was out directing. Who knows, maybe his show is struggling and he will end back up at CC. Of course, I don't wish that on him but there is always going to be a larger viewer base on cable channels than on premium cable channels.