I've only done Von Bon since Red hasn't really been on since then, but even though we ran out of time for him in the final stage, he's not that hard. Most of my deaths were dumb mistakes like misjudging my jump or something |: Haven't done Pierre yet but so long as you remember how to respond to his skills and not hit him with the same colour he's not hard either.
Queen is still unavailable isn't she? Not sure I wanna fight Vellum, either... Seems like a gigantic pain in the ass.