Well Manaphy's departure from OU is unfortunate. While I genuninely don't think it was the problem that needed addressing right now, the majority rules and I have to accept that verdict (coming down to the very last vote to decide it's fate, wild ride).
Let's start with the losers of this:
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Good news is that it's pretty much low tier mons that were seeing usage large in part due to Manaphy, which is a sign that the decision was admitedly overall - a healthy one. Shedinja will persist and still maintain a place in the tier, but being a lot less critical for stall - which is good. Sticky Webs offense losses their arguably most defining component, and while there are still plenty of options available they definitely will miss Manaphy's reliability and potency. Same goes for dual screens H.O. Mantine is definitely the biggest loser of this change and it's usage/viability will greatly reduce - if not fall out entirely; Manaphy was almost the sole reason this thing was being used for.
Funnily enough, the Stall playstyle is actually a big loser in the departure of Manaphy. That may sound insane, but as folks have talked about at some length over the fast few weeks in this thread: one of the biggest reasons for stall's recent prominence and dominance has been it's ability to handle threats like Manaphy. I bring this up because of the unforunate common, uneducated arguement that "smogon bans anything that beats stall" really isn't true. This is not directed at anyone that's been posting here, but for the potential possible person who decided to view this thread trying to figure out why Manaphy was banned: I encourage you to go through the past couple of weeks to read through what folks have been saying, it might change your perception.
Now for the winners:
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Clef is finally freed from being pigeonholed into it's sp.def unaware set now that Mana is removed from the equation. It still has reasons to be ran, but not as mandatory and can be transitioned comfortably now into phys. def varriants to better hold off sweepers like Chomp, dnite, weavile, and even certain varriants of Scizor. It'll also be nice to hopefully start seeing Magic Guard coming back
(knock on wood, though watch me eat my words later as I get sick of seeing clef everywhere after a few months). Blissey also having one less special attacker that can break it to worry about is nice, though unfortunately it's need for running CM is still forced upon it by Gengar (can't wait for the suspect, get this thing outta here). Defensive waters like Empoleon, the slow twins, Tentacruel, Quag and Gastro notably become more consistent walls that don't have to worry about letting Mana in for free and using them to boost up. Rotom's scarf sets remain potent but are less vital, which is nice. We might also some lower tier mons find new life in tier's viability with Mana gone, time will tell. Overall there were a lot more big winners than there were losers.
This also arguably helps balance teams, but... where are they still? Let's talk about that.
Balance:
The big "mission" of the recent tiering action has been, generally, trying to bring back balance into relevance as a playstyle.
Will the Manaphy ban bring balance back? By itself: no. It's nice that defense can breath a little easier and diversify a bit more with their sets and viable options, but we still haven't fixed several key components that have held the playstyle. Blissey's almost mandatory presence for protection from arguably the most dangerous mon in the tier - Gengar - still has the style pinned down hard. Until it's removed, I don't foresee balance resurfacing to relevancy.
I'll also bring up Latios's impact for a sec. Manaphy leaving the tier doesn't change a thing about it (I guess 1 less reliable partner that was often paired with to overload their shared special wall checks) and the Scizor infestation continues. Though I wouldn't say this is personally affecting the nature of balance directly, at least far less than Gengar is. Ios is fantastic against offense, on par with gar, but against common defensive pivots, walls, and hard stall it struggles - these types of teams really doesn't care about ios. There's a lot more that reliably defensively checks it, which is not the case for gar: Plot gar destroys offense and stall alike. For the moment Ios is "fine", but my opinion has gone from firmly DNB from it's previous suspect to mixed. Once Gar is removed from the tier and we hopefully see the meta stablize, assessing the blue dragon's influence on the meta will be much easier and we can come to a more concrete conclusion. Also Zam to a lesser extent.
I'm not thrilled by the removal of Manaphy, I don't think it was the right decision for the right time, but I can respect it. The impact knocks H.O down a peg, and stall to some extent. It frees up defense a bit to run a slighly wider variety of options which is generally good too. But it's not gonna bring about the rapid or major meta change a lot of folks want, for that we're gonna need Gar out of the tier. I eagerly await the date for the spooky ghost's suspect to commence so we can start making some real progress.