I do not think DK should be higher than 18th, and I made an argument awhile back in the tier list thread about why I think he shall stay as 18th or drop 1-2 spots. I think a lot of times, when people argue about placing DK higher, they forget to take into consideration where other characters would relatively be placed.
Meta Knight
Snake
Wario
Falco
Diddy Kong
King Dedede
Marth
Mr. Game & Watch
Pikachu
Olimar
Ice Climbers
R.O.B.
Kirby
Lucario
Zero Suit Samus
Toon Link
Pit
Donkey Kong
Look at the characters above DK. How many of them do you honestly think DK should be over? He's not better than anyone currently above Lucario (Kirby IS debatable, I don't think Kirby is that amazing to begin with but that's just me), he's most likely not better than ZSS unless she gains a really hard counter somewhere down the road, Toon Link you would have a hard time justifying putting DK over considering TL also doesn't have a LOL matchup like DK has against Dedede (even though MK is bad for TL, MK vs TL is more like Wario vs DK.), and even Pit you could make a strong case for staying above DK. I know that Pit is definitely a better character than DK if planking is completely allowed.
DK is not bad. He may be better than a lot of people gave him credit for. The problem is that most characters right above DK were ALSO underrated and have validated their spots/potential rise up the list. DK really hasn't.
DK has some pretty good results on the EC, but this doesn't entirely validate the opinion that he should rise. The infinite on him is banned, and some places have already started/are really thinking about starting to ban Wario's CG on DK (which, while I thought banning the Dedede infinite on DK was already stupid, that the idea of banning Wario's CG on DK that is NOT an infinite by any stretch was flat out ********.) So obviously when you make rules that basically cater HARD to Donkey Kong (Wario's CG on DK is banned, not Wario's CG on other characters, and Dedede's infinite only arguably interferes with the viability of DK alone, you can basically call that catering to DK and not other characters who face similar problems), it's not hard to assume that his results will be artificially inflated.
With that said, I think he is fine where he is. Peach you could argue for placing over DK, but everyone else is most likely gonna stay under him.