Mercer is eligible for the RWC squad. Not just post RWC, although I wonder if he feels as though his move to Gloucester (to make himself eligible) is a bit riskier with a new man in charge for England?
Back row wise, we're spoilt for choice which unfortunately means good players missing out and it's hard to know what the best combination might actually be. Perhaps it ought to become more of a horses for courses/game by game piece, but I would generally prefer to see continuity in style and personnel.
I'd like to see Willis, Curry and either Dombrandt or Mercer as a trio, with Earl providing impact from the bench. At the same time I'm not against a more classic blindside. I'm fully converted on Lawes as a 6 and I was impressed by his captaincy in Australia. If/when he's fit, he's surely still in the mix. I think Borthwick will like the idea of Lawes or Hill at 6 which might mean Willis is more of a deputy for Curry.
I really hope we move on from Billy. He's still a good player, but I think he offers the least out of the options at 8 nowadays.