Nafereus

Let's be real, Rev really doesn't have anything to master, she uses summons that are set and forget and her ult is also just as set and forget, Executioner is pretty alright, his deflects are so catch all that you're right he's not hard, literally everyone gets bleed weapons and Rev is the other person who has good Arcane and can make the most of it so that's a bad example if you want Rev to come across as not that strong, I think the hardest is Guardian or Recluse because they require you to learn things.

Guardian I think is the hardest, since his blocking is not as easy to use since you can still get hit if you dodge in the wrong direction, his ult is also very good to hold down if you time it right letting your team go ham when they would normally not have the chance and Recluse has the micromanagement of the cocktail though that is basically just slight difficulty curve and once you know what they do it's really not that bad.

That being said, it's not like any of them are complex and none of them don't have a little secret to learn like using Wylders ult as a extra jump or that his grapple has really good interrupts as it counts as a thrusting counterattack.