Yep sound list, only thing is drop the Crown, as a charging Nazgul on fellbeast gets 3 attacks anyway. The Witchking on fellbeast with Crown charging has one more attack. 30 points for one more attack isn't worth it IMO. Instead armour up your Fellbeasts, (20pts each) but it means they are tougher to kill! You save 30pts + the spare 10pts which is enough to upgrade 2 fellbeasts. Then why not upgrade the other 2 by taking a slightly weaker Witch King? Say 3/14/1. The Witch King shouldn't need to be spending his fate points if he is charging and winning those combats! Knock down and double wounds. Then 3 might for calling Heroic combats. Looks pretty powerful and now all your mounts are Defence 7! Strength 2 bows and strength 4 attacks are now not as effective.
Also one point about the Tainted, if an enemy calls a heroic move (likely to counter your charging ability) then warriors within 6" of the Tainted cannot take part, therefore your other 3 wraiths will be free to charge should you win priority. Effectively if an enemy hero uses a might point to charge the Tainted, then you don't have to content the point as all nearby warriors won't take part in the Heroic Move. This leaves your other 3 Nazgul free to cause mayhem! This also affects Stand Fasts and don't forget his Seeping Decay rule. Personally I'd take the Tainted over the Undying as you want Fighters over Spellcasters when they are mounted on Fellbeasts, but that's just down to style of play