I just think it's silly that some games get called ARPGs but then Skyrim and The Witcher 2 don't even though you're button mashing or doing combos in those games.
Haven't played Witcher but, for stuff like Skyrim, I'd say the difference is that in an ARPG like Borderlands or Torchlight the action IS the game.
To go in the other direction, Assassins Creed 4 was full of button mashing, equipment upgrades and even a shallow crafting system but no one* was calling it an RPG. FC3 has button mashing, crafting, and skill trees but I never saw anyone playing it refer to it as an RPG. Well, I suppose that one idiotic review calling it "Skyrim with guns" implied it.
(*Well, no one I saw. I'm sure someone out there has a blog calling it an RPG though)