De3 victims as topic now? Cool
DK is a good character because his playstyle can be played properly. DK has tools for approaching, and enough range and power to get along without having a projectile. If DK wouldn't be infinited, he'd be represented far more.
Luigi is actually pretty good. He would need more range or priority, and his projectile could be slightly better, but overall I'd say Luigi is a great character, especially with his ridiculous NAir and his combo abilities.
Bowser's moveset is actually wrong done. Bowser has a defensive playstyle, however, he lacks a projectile to actually enforce that defensive playstyle. Bowser has to approach at half of the cast, and approaching puts him into a disadvantageous position, thus making him vulnerable. If Bowser had a projectile to enfore approaches, he'd be High Tier.
Mario... I don't have much experience with him, but... He actually is a very balanced character. The problem is that so many other characters are excellent or good, resulting in the average being Low Tier instead of Mid Tier. Funny enough, I think that the game is oddly balanced except for the worst 6 characters (Lucas, Samus, Link, Jiggs, Ganon and Falcon).