User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-190.92.7.204-20150612220839/@comment-5961531-20150618233222

I say that because we've seen what powers the Mark grant you, enhanced strength and telekinesis. Cain has both of those powers already by just being a Demon. The bulk of his power comes from him being an already powerful Demon.

As for Dean, he only ever showed enough strength to overpower a nameless Vampire, and he struggled with that. Castiel was only trying to subdue Dean. If Castiel decided to go all out it would have been a different story. Don't forget, at the start of season ten, Castiel already managed to subdue Dean while the latter was still partially a Demon. Plus, Castiel had a borrowed grace at the time. In conclusion, regular Angels are still physically superior to Mark wielding Humans.