The problem I see with this game is the fact that, since +++ and ++++ traits were scrapped late in development, these challenges were obviously meant to be completed with these super traits in mind. Due to them no longer spawning, their rarity is also unknown: Current ++ could have been ++++ in the past (which would make sense, ++ traits aren't very easy to find even with a Level 10 Special Tree).
I don't think the Atk trees will even make a different at this point. With the limits in place, you basically need to get by with multiple amazing Dialga / Mewtwo resets to spam Roar Of Time / Psystrike (I also think Secret Sword is vastly underexplored and it is one of the best moves in the game - backed up by the relevant traits, its usage in boss battles is fantastic), clever usage of Endeavor and abusing the fuck out of it for the giant bosses to even have a chance to complete WCSX on hard.