I'm still intensifying over here on that knowledge drop on Robin I was supposed to get from you when said question was passed along @
Nairo
my hopes were officially raised and everything
I'm no Robin expert like Nairo, but have some experience with her, and she really isn't bad. She just requires patience and control to use well, she can't spam and she can't get too greedy. Her defensive game is one of the game's best, between three versatile projectiles, a good grab, a command grab, and the excellent range of the Levin Sword. Her aerial game is among the game's best in terms of power-to-speed ratio due to her very quick nair, lethal uair, effective bair and dair spike and her quick pressure-reducing fair. Her smash attacks also possess very favorable hitboxes and excellent power.
Her mobility is poor, but that's not a problem for her because she isn't meant to be offensive, she is a defensive punish character and has good spacing tools for exactly that reason. Thunder + Arcfire core is better than you give it credit for. Yeah its too slow for Sheik or Diddy, but every projectile is for the most part, and Robin at least has good survivability and smash attacks that can tip the scales (pun intended) on a good read.
Robin is not top tier material, but she is definitely not bottom either. She's a solid mid, probably close to where Marth is sitting. She can projectile camp and punish heavyweights all day too.
On a different topic, I agree that Wii Fit Trainer, Dedede, G&W, Samus and Zelda are probably the "bottom five" everyone seems to talk about. Bowser and Charizard probably narrowly avoid bottom five, and Dr. Mario, Lucina and POSSIBLY Ganondorf, depending on how the meta evolves with customs, probably come in next.
The overall balance is still good, but the very first time I used those five I noticed immediate flaws.
Zelda is weaker, inconsistent as hell, Din's was nerfed for no reason, Phantom doesn't hit properly much of the time and she still can't combo well, despite clear efforts to make this easier for her. SDI smashes (why is this still a thing in a world of flawless foxcopters and Mach Tornadoes?) and while faster and heavier, she's still too easy to KO. Credit to Nairo for his success with her, because even Brawl Zelda was better it seems.
Wii Fit suffers from a poor, gimpable recovery and terrible range and hitboxes on her moves that make her whiff continuously, forcing her user to play exceptionally well to land good strings on a good player. Her attacks are also too laggy for how hard they are to land.
Dedede has atrocious mobility and his aerial game is too slow, plus being able to reflect gordos takes away his otherwise stellar defensive game, since he lacks a safe projectile.
G&W, one of my old favorites was nerfed way too hard, losing kill power on everything, still being a super lightweight, losing many great hitboxes on signature attacks, having his damage output reduced and nerfing his Down B options. I like his new speed and better combo ability but he needs at least more power on fair and a bit more damage on nair and bair (his bread and butter attacks need to be really good).
Samus still suffers from a terrible neutral game, a lack of many combos, inconsistent kill moves that can be SDI'ed, asinine priority, a loss of good zair, dair and DSmash. She's arguably still worse than Brawl despite her buffs in other areas. In free-for-alls she's probably amazing though.