K the point of Rancor is so that if the fellowship double moves I get to hit them once more with a round of evil wounds.
Sneering Fellow doesn't seem to be worth it as Nazgul don't roam much as is and it would be difficult for a ranger deck to do much against The Witch King as he's strength 21. Also the Black Flail is there to counter tank decks and as I know someone who can get his Sam to strength 22 it would be helpful.
If they can't beat your WK in skirmish, they won't double, trust me on that
. Ferny is good, because it is a +4 pump for any minion (you chose how to assign it, just like when you have more minions, than comps), and a good ranger deck would kill your WK with
IB, also you can assign it to the RB (and against any gondorian RB or Gimli it is pretty good for only 3 twilight). I think that conditions can be much bigger problem for this deck than possessions, so I would definitely go with
The Pale Blade instead of
Black Flail, but I guess you know your meta better. If you are worried about big tank comps, such as
Durin III, play
Wormtongue, that is by far the most evil way to deal with them imo.