Sonic's dair isn't an OHKO. But if he spring spikes you right after it, then you are gonna die. Falco may be top tier, but he doesn't feel cheap to fight. I've never fought a Falco that I couldn't beat. So far there isn't one. Seeing as the characters I use are countered by Falco, this should mean that he isn't over powered. Though I suppose top tier and OP aren't the same. Top Tier is where we want people. Over powered is not.
You think your characters have it so tough. Sonic Falco is probably even or pro Sonic, Falco Link is slightly pro Falco or even, and the same for TL. You can't spam projectiles, but Link's range is more than enough to out-box Falco with good spacing, and the same is true for TL.
In my matches against BC's Sonic, I FREQUENTLY got OHKOed by D-Air. BC didn't even use the Spring double spike most of the time. I knew Sonic's D-Air was OP when it killed my 'Dorf at 8% damage -- I was mashing Jump immediately after getting hit by it, but 'Dorf could not do ANYTHING but rocket downwards. My other mains were affected the same way.
Is the meteor cancel penalty window from vBrawl still present???
That would explain the issue. If not, that's a load of garbage that Sonic's dair does that. Falco dair can't do that at 50%.
I have to say that the characters you used have natural weaknesses to getting spiked. Not only that, but there's nothing Sonic can do to force you offstage at 0%. Testing side smash and throws from 0, Sonic doesn't have enough time to get where he needs to be to spike you to death. Although the move DOES kill Ganon from 0, Ganon offstage at 0 is ALWAYS Ganon's fault. If you're keeping your distance from Sonic like that you don't know how to fight him.
Then fix the meteor on Sonic - Dorf's job is to OHKO [WP], not be OHKO'd. And that happens if you chase offstage, which is silly that he gets a free zero-death for a single mental mistake that requires very little execution on Sonic's end [even Falco generally needs triple dair or two sweetspot dairs, and also has to avoid getting hugged]. Also dair -> footstool -> spring is really really stupid zero-death he has.
I'm realizing some of this stuff only now, but Sonic is probably actually really really good if the player is patient with KOs. But people want those 100% KOs which is why we all label Sonic as "Bad" when he's not [and that silly dair spike gives free 50% KOs].
Can we give Spring purely horizontal KB? Yes it will still screw over some recoveries, but it won't auto-death from the dair -> footstool combo [which can KO anyway]. Then there is actually a reason to try recovering instead of just laughing/being salty and starting the next stock/match.