While I think the game is proving pretty well balanced as it is across the board (but not in some cases... yes, of course, Diddy Kong...), I don't think it's great that balance patches aren't really in consideration, supposedly.
It would be one thing to say that they're going to try to keep changes to a minimum, but saying that they're basically going to be avoiding any changes unless something really awful is found? I think they should at least plan to reserve this verdict until they've watched the game unfold for several months, at least.
It hasn't even been a month with this patch, after all...
As for Diddy Kong himself, I think he could use a nerf, but he's not untouchable. There are other characters that would fill the top tier if he were nerfed down a bit, and things would still be basically the same for most of the characters... though, personally, I do think his shenanigans are pretty dumb.
Should Diddy be nerfed? Probably, I'd say... but there are a lot of characters it wouldn't help even if it did happen... we need more buffs like what happened to Shulk to help some characters who are having a hard time...