I think "Bottom tier" should refer to how picking that character means you could hardly make it harder for yourself to win consistently.
Fair enough. I think high and high-mid should be similar-ish though. I disagree with calling a lot of the characters currently in tier 4 just "mid" tier, since I think they're high-mid tier (most of them). With tier 3 I think 3-4 of them might be good enough for high tier. This could, perhaps, be solved with a few more rounds of voting if we decided that tier 3 is, in fact, high-mid tier rather than lower high tier that some of us expected it to be.
Let's compare with the 4BR tier list: Ness, Captain Falcon, Corrin, and Lucario were in high tier there. I think at least Corrin and Lucario deserve to be (for comparison, ZeRo put Lucario at #12 and Corrin at #16, slightly too optimistic in my opinion).
If we consider ZeRo's "Upper" tier to be roughly the same as "high-mid", then Olimar, Yoshi, R.O.B., Luigi, Bowser, Shulk (!), and Robin deserve to move up. I am unsure about Yoshi and I disagree about Shulk, but for the rest I'm inclined to agree that they are high-mid tiers.
So, if we do settle for 3 as high-mid, 4 as mid, and 5 as low-mid, then I propose we do the following (in the following voting period): Move Corrin and Lucario (and maybe Captain Falcon and/or Ness) up to High tier. Move Olimar, Robin, Donkey Kong, Bowser, Luigi, and maybe Yoshi and/or R.O.B to high-mid tier. Maybe move Wario and/or Mr. Game & Watch to mid tier. Maybe move Samus up to Low-Mid tier.
The tier list might look like this (tiers not in order):
Top:










High:













High-Mid:









Mid:






Low-Mid:






Low:








Bottom:





Every character in High tier has a good shot at making a good run at a Major, and an even better shot at doing well at smaller tournaments. High-Mid have some pretty good uses at majors as well, yet they are not as good as High tiers. Mid tier characters can do well but generally struggle to be consistent, and Low-Mid tiers are generally not worth it but can have some niche use. Low tiers are generally bad for majors but can have some niche use, while Bottom tiers struggle to get results at large tournaments.
Aaaand then we're back to high tier being large, which is why I helped "split" high tier into two to begin with. Oh well. And yes, I personally think that more than half the cast is High-Mid tier or higher; the game is decently balanced. With that being said, I am of the opinion that every character could theoretically be High tier, although in that case a tier list would likely look more like "top 10 tier, top 20 tier" rather than "Top, High, High-Mid".