It isn't a problem for it to clang with jabs and tilts. Most dash attacks do that already. It's the fact that it clangs with SMASH ATTACKS that I have a problem with. That's a sign that it has too much priority. Mario is already pretty solid a character, and he doesn't need so much priority on a move that's supposed to start into combos. He can already chain 3 usmahes from 0%, and combo further into higher damage. His dash attack is already fast, has a lingering hitbox, and can be used to follow up into more attacks almost immediately (not even counting the ridiculous chaining into itself as mentioned.). Why does it need to have such high priority when it's purpose is to start combos, and not cancel out pretty much any attack? Might as well raise Diddy's priority too, since his dash attack functions almost exactly the same.
As for opening his opponents for aggressive play, he already has plenty of trickery and versatility to accomplish this with his Fludd and his Fireballs, both of which are a legit pain in the ass to deal with, but I have no complaints with them, as they both have their counter-plays. I just don't feel he needs more priority on his dash attack than even powerhouse characters, cause it doesn't fit his style, and it just isn't fair.