Thor, I don't know what you are talking about. Have you played Mewtwo? The bair to outspace Jiggs? Whine alot? Dude you would be lucky if outspacing was even a option. If jigglypuff players can deal with Shulk and his bair why would it be different Mewtwo's slower and weaker bair. I fought a level 8 jigglypuff while practicing random CPUs and that fucker gave me hell. And it was only jigglypuff. I usually destroy those computers. Then I fought my friend who is a legit jigglypuff main. I don't even want to talk about how dirty that was.
Well Shulk's bair is super laggy - the real problem in Puff Shulk is working around Shulk's fair.
Yes, spacing around it is hard. That's how Smash works. Puff has to space around Fox usmash in Melee and Fox has to deal with Puff's bair beating or trading with everything he does that isn't the lasers [lasers...]. Every character has to outspace Puff and Puff has to outspace everyone else - I don't mean that you necessarily have more range, I mean play the spacing game so you are landing your hits while being mostly safe from theirs.
And how the heck did a level 8 CPU give you trouble? I had no problem cleaning them out [level 9s are obnoxious but still perfectly doable], unless Wii U Ai is different from 3DS AI and you used Wii U [since I haven't really fought level 9s on it when I was at home and I don't have it on me].
Maybe I'm just unclear on exactly how Puff can devastate Mewtwo, but if you're getting rested, you got outplayed [she doesn't really have setups into it besides jab locks from what I know]. Sure Mewtwo maybe can't combo her as well, but you do have a solid projectile, a kill throw that KOs her early, and usmash should beat out every one of her landing aerials, while also killing her probably around 85% or earlier [connect at 85%, she should die at 101% if it's fresh]. I'm headed to a tournament today so I'll fight some of the Puff players with Mewtwo [in friendlies, he's banned from this event because newness] and I'll see if I change my mind or [hopefully] if I can try to offer some insight into the MU as I see it.
But hey, I've been wrong before, so if it's really that awful, we can pray for weight buffs and a more disjointed bair or uair [those two things alone would probably make him seen as a lot better, since as of now I don't think either of them is disjointed much if at all]. Or a dthrow that combos into stuff.