HOWEVER, OTK decks should be punished by aggro decks since combos take time to assemble in your hand. You shouldn't be able to OTK on turn 4 no matter how good your draw was.
I'd say god hand, very rare T4 combo with coin is fine - the issue is more that it seems to be reliably going off T5/6. OTKs should, 100%, be punished by aggro and tech cards most of the time (speaking as a combo player, though I tend more towards jank these days - I'm playing a STD variant of Mozaki at the moment, which without the apprentices is nowhere near broken, though I spent a lot of time playing Freeze when that was an actual deck, unlike now, as it's been creeped. In WIld I usually play three-minion Malygos Shaman). Very occasional nongames that are faster than interaction aren't a probelm - it's reliability, IMO.
I've played utter jank that could T4, which I think I never managed in a few hundred games before Barnes got nerfed (though I did a T5 combo once or twice). That particular deck is fine because it's not reliable going off that early (I think it was a T3 coin barnes hitting ancestor's call, one 2-drop burn and three one-drop burn, then topdecking Maly, or hitting maly and four of (all four 1-drop burn spells + ACall), with the fifth being topdecked. Utterly ridiculously low chance situation, given how the deck mulligans for draw, not combo, and that you can't use draw as that's 2 mana overload or 3 mana, so too slow for this) - or even reliable going off at all! Also a deck that's weak to almost all of the possible interaction (Rat, Loatheb etc.).
Broken eternal formats are a very easy thing to produce that take attention to avoid - look at MTG. Legacy/Vintage there are fine (generally - not heard of them being broken since I stopped playing! There's the occasional stupid card printed, though), but that's almost entirely down to one card (Force) allowing interaction (To the extent that jokes were that JTMS, a few hundred quid card on release, was good in legacy mainly because it was blue and thus could be discarded by force, despite power level of it being ridiculously high.). Without counterspells - specifically zero mana counterspells, because those are fast formats - you'd end up with metas full of oops/belcher et al. With zero mana counterspells, you get slower combo that plays around force, going off T2ish, which then get preyed on by stuff like D&T with Thalia or other taxing, and so on. One card makes a healthy format there. On the flipside, they tried printing Misstep, as counterspell for 1 mana that technically cost 1 mana but you could pay life. Because there's no downside to it, and the best answer to a misstep is your own misstep, it was everywhere. Even goblins, who, despite being far more tempo than aggro, have no place for counterspells, ran a flipping playset of it until it ate a ban. I don't think that Blizz really pay enough attention to Wild to make a healthy format, and cards aimed at Wild are more likely to be a misstep situation, IMO.
But hey, it could be worse (maybe not much, though). We could still have Hysterical Tillers everywhere. That was... not a good meta in any definition.