A few to many Ghiest around at the moment for Nellie. Plus I think Kazayan is a slightly stronger card. While you may have the potential for a 1 power difference on Nellie, the Uppers bonus makes that slightly less necessary.
You might also want to consider changing Vito out for Desmond, or even a 3* like Sharon, Moses or Gianfranco, that would allow you to keep Nellie and upgrade Oxen to Kazayan.
I have a lot to comment here.
Firstly, Montana + Uppers is not a very good combo at all, they practically do the same thing. Old gen used to be good in DTs, but never in ELO. Just my opinion.
Secondly, if you are using Uppers, imo Rubie and Oxen are MUSTS. Rubie is essentially Vito with reverse stats (so slightly worse?) but a whole star less. Even with 5 power, top card in meta with that valuable SoA. Oxen is just very solid.
Thirdly, Wendel > Jose Star and all the other 2*s, in elo at least, SoA is invaluable.
Vito is crap. Desmond is 1000x better.
When it comes to Uppers 4*, you are actually stuck on a 3 way competition: Maurice, Nellie, Kazayan.
Maurice is almost a Marina, not quite a Marina though, pretty good card.
Kazayan is Zinfrid with a different, and a heck lot better bonus. semi-unreducible damage.
Nellie is a mini Herman, which is banned in elo.
Personally, don't quite like Maurice, never a big fan of 4* reducers.
Kazayan vs Nellie comes to rest of the deck, and whether that one damage makes a difference. Edd Cr and Desmond both has 5 damage, so its actually nice here.
Thats my input
Depends on your playing style. I prefer Nellie because it still is a 6 damage card against SOA and will force your opponent to 2-3 pill over no matter what. Kazayan is great in DR heavy weeks. all in all I'd go with Nellie because she fits my style greater then Kazayan
Also like oracle said..Montana+Uppers isnt a good combo to half with. No synergy added just same strategy.
Just remember that if you have both Oxen + Kazayan in hand, it's a hard bluff to guess. Kazayan is better in halves normally, with Rubie don't overpill unless you need to. She wasn't designed for that purpose. Desmond is ten times better than Vito, plus when you have Angelo + Wendel what's the point of Vito?