tbh none of the 'counters' really fit on offense per se (aside from maybe klefki, manaphy and gyarados), so you have to rely on offensive pressure to check it. heck, even klefki gets bopped by hpump, while greninja can just switch out to thundurus or something to block twave.
i've been messing around with the ladder atm, metagross seems like a rising threat without greninja. it was already good before, but greninja could check it with dark pulse while metagross's bullet punch is resisted (so greninja can still take a hit). i'm not sure how i like this considering it seems a bit harder to play around, but greninja himself is pretty cancer and i guess we'll get to metagrossite when it's really stupid enough (and i stop playing at 2am so that i wont choke like every 3 games)
leaning towards ban on greninja though, reasons are mostly because he kinds of fucks over offensive teams and running the 'counters' are pretty much just non-conducive for offense tbh. while i never really found an issue with greninja since i usually play stall, greninja is still pretty ridiculous since running the wrong counter to the wrong greninja often means you get screwed over (chansey can only take so much a beating). i mean, i could run tentacruel to deal with greninja, but getting screwed over by extrasensory is stupid, especially when its actually really viable as hell.
the problem is not the 4mss, it's what the fuck you're supposed to do when you see a greninja. greninja could very well be running a move that fucks you over, no matter what you pack. shit like esense, hpfire, grass knot and hp fire/electric are all pretty cool options, and you never really know what greninja is running tbh beyond ice beam (and maybe gunk shot or dark pulse). you can pack a 'counter' to greninja for all you like, chances are it will get screwed by another greninja variant.
this is a bit similar to mega lucario, who basically fucks over counters if they go into the wrong set, but the counters here aren't that far apart this time, and some do actually overlap between sets so its not as bad. the difference is however the coverage that pretty much stretches ad infinitum and the speed tier that literally shits over every single non-scarfed/mega pokemon in the tier. 122 is fucking godly, discounting megas, there are only 10 pokemon that outrun greninja, and all of them either suck (pretty much all of them except maybe NOIVERN) or are just badly outclassed (see NOIVERN), the only exception being TF who obviously can't switch in and doesnt really care about speed in the first place due to gale wings (outside of dodging water shuriken)
greninja isn't unbeatable, yes, but it's an issue when you are going to end up crippling half your team just to beat it tbh.