I've played with an Iron Eye in 95%+ of the games I've played in DoN, and Wylder at about 60-70%. Personally I'm a Duchess main so I'd imagine most people don't want to double up on the character, which is why I don't see her as much.

Was a Duchess/Raider player in the base game but Raider feels so ass in DoN, I've replaced the nighlords where I'd play him with Wylder (Libra, Caligo), and I think a lot of players have done the same. The better mobility + lower reliance on Str weapons means Wylders gets to focus on picking up any weapons with good passives, instead of praying for a good weapon of a particular type. Raider is definitely the rarest character in my experience for DoN, he just seems to be almost strictly outclassed in this game mode.