For the complaints about Mario and Luigi's fast Nairs, they're not the only ones who can do this. Everyone knows Yoshi can and we definitely shouldn't forget about Dr. Mario. Characters with frame 3 Nairs include: Dr. Mario, Falco, Luigi, Mario, Mii Fighter, Villager, Pac-Man, Pikachu, Sheik, Yoshi. Remember this thread:
http://smashboards.com/threads/list...-initial-frame-to-slowest-frame-speed.388564/?
The notorious ones are (Dr.) Mario, Luigi, and Yoshi, but we've seen the OOS Nair Pikachu abuses, the gliding Nair Villager throws out unpunished, and Mii Fighter's Nair has been noticed as really powerful. Everyone, but Falco can interrupt fairly well by spamming Nair. Why not Falco? Look at the list, of the 10 characters, only one has a multi-hit and not a sex kick Nair: Falco; of those 10, Luigi and Falco have the slowest air speeds; and of the 10, Falco, Sheik, and Mii Brawler are the noticeable fast fallers. Falco can't spam Nair to get out as easily since he has to connect the entire move or the final hit to get enough knockback which essentially makes his Nair frame 21 since his Nair doesn't have autolink angles - main reason why certain multi-hit moves like Falco's Fair and probably Fox's Fair connect so well - like Zelda's or have a strong, single hit like Peach and Ness. Fast fall speed and poor air speed just makes it worse since he'll get comboed quicker than Sheik who has good air speed to drift out and Luigi who's a floaty so he can drift out as well.
The frame 2 Nair guys, Little Mac and Mega Man, can mash out Nair to interrupt combos, but they're not as good since they lack sex kick properties to surround themselves with a hitbox.
Frame 4 Nairs can probably interrupt combos too, and the ones that have a frame 4 include: Fox, the Pits, Wario. Oh, and there's Diddy's notorious Uair, (Dr.) Mario's Super Jump Punch, Little Mac's Rising Uppercut, Marth and Lucina's Dolphin Slash, and unsurprisingly, you don't need a quick aerial to interrupt combos. Remember Captain Falcon? A frame 3 jab that eats through everything and if you somehow drop the ball, Captain Falcon, Ganondorf, and Link can all frame 7 Nair you or Jigglypuff can Rest counter you.
Players shouldn't be mashing buttons; the attacker shouldn't go on autopilot and the defender shouldn't be panic-mashing. At the same time, yes, it's kind of stupid that some characters can get mashed-interrupted because certain characters have really fast moves, but at the same time, you probably shouldn't be holding rapid jabs for that long and if you're going for the same combo over and over, I expect the other player to catch on and counter even if it means by mashing a move to interrupt.
Here's the thing, the main "culprits" to Nair interrupts are (Dr.) Mario, Luigi, and Yoshi. Is a frame 3 Nair really necessary to their moveset? I wouldn't say so, especially since Luigi's can cheese you out since his Nair is really strong, but do they need to be nerfed to oblivion? No. If anything, they could end up with frame 4, 5, or even 6 Nairs and they wouldn't be severely hurting. The other question is who are getting screwed by these Nairs? Ike probably isn't since his Ragnell isn't part of his hurtbox, Captain Falcon probably isn't since he can just bait a Nair or airdodge and punish, and Samus does not give a damn when she can Charge Shot your dumb Nairing butt. From my experience, only Falco is screwed by this, but Falco is screwed by everything. His jab gets Naired interrupted by all of them, jabbed by everyone who has a frame 3 jab and below, grabbed by Luigi and probably more, Dolphin Slashed, Rested, Super Jump Punched, and more. Link, Captain Falcon, Ganondorf and more can fast-fall Nair him before he can even input a move to hit them, Rosalina, Palutena, ZSS, and more juggle him to death since his air speed and fall speed make him the greatest juggling pin that ever lived, and Mr. Game & Watch, Jigglypuff, (Dr.) Mario, Luigi, and Fox can cheese so much damage with one move: Dash Attack for Mr. G&W and Jigglypuff and Utilt for the rest. It's one character who's screwed, big whoop.