If the deal is right, they are all expendable.
I am sad to say I agree. The core or players I would not trade consists of Berrios Rogers, and Polanco (at 2B). I really value Garver's steady improvement so I am ok with him being considered part of the core. Buxton and Sano have so little value right now that I seriously doubt a deal comes along that would make sense to give up on their upside.
If we could get a return representative of the best of Rosario, great. His lack of plate discipline drives me nuts. Aggressive is fine. Astudillo is aggressive but he does not swing at pitches 16 inches off the plate. It does not appear to be not pitch recognition. Therefore, it should be correctable. He should be getting better with experience but it appears to be getting worse.