This whole post doesn’t actually discuss any counterplay to Ogerpon-Wellspring, instead opting to incorrectly label it as a Tera hog and claim it’s predictable (what does this mean when 3 moves hit the entire tier short of Amoonguss?).
I don’t even think there’s an issue with saying you don’t find it to be a problem, but what you’re saying doesn’t move the needle at all. What do you use on your balance and offense teams that makes it “almost never an issue”?
Well, I said what I think. I didn't know you were looking for anything specific when you asked for what we think. Nor did I plan for my largely neutral opinion on the thing to
"move the needle" for you. I called it predictable because it is generally going to be STABS and a combination of Swords Dance, Encore, or various coverages, which are generally one or two of several staples. You don't have to worry about a strange item or Tera typing. My point is it does what it does very well, but you know exactly what it does. Even something you think of normally as very predictable like Raging Bolt can entirely flip the expectations you had for it with a different item like Grassy Seed or Assault Vest. Waterpon just doesn't go outside of expected norms. I'm not too worried about most of the variables when I face it compared to most other threats in the tier. I don't see what is controversial about that.
I said Tera hog because all the Pon forms need Tera to maximize its abilities by design. You can decide to not Tera, and you probably do that in matchups that it isn't as strong in, but you aren't getting the max potential of the mon by doing that. And you are leaving some wallbreaking potential on the table by not using the Tera. I mean, it's just an objective truth from a game design standpoint that its mechanics are centered around Tera.
As for matchups, well, I think it depends on how you build and what style you play. Most people have already touched on Wellspring being more of a problem for slower teams. So I didn't feel like I needed to go into more specifics. I'll at least try to give you a picture of what I do.
Lately, I use a lot of Rillaboom teams, faster mons, or priority like everyone else on offensive teams. I use a lot of fast things so Oger damage is often limited. I have also used the base form Oger a decent amount. There have been a lot of Dragons on my teams because many of them are good in the meta. Play Rough is a problem for Dragons, but not Gouging Fire. D-nite sets up on Waterpon with Multiscale. Generally, there is also at least one poison on my teams like Glowking, Glimm, or even a rare Geezing. Hazards are common on my teams. Glimm got more common for me again because it helps me deal with Gouging Fire a bit more easily. I don't use Zama much so I don't know how that does into Play Rough. I assume it must be decent into Pon, right?
Anyways, most of my teams are gonna have a Poison type, faster threats/priority, and at least one Grass and/or Dragon type. I hope that helps you get a clear picture. I'm not saying what I do is better, either. It's just a result of the styles I play and how I tend to teambuild in a threat saturated meta.
If you were to build your teams with something like Prim as one of the defensive staples, you might struggle with Pon more. And its great into a lot of the rest of the tier. I can make that case about Gouging Fire and numerous other threats, too. Balance generally doesn't have room for defensive checks to all the threats in the tier. But that's not specifically a Waterpon problem. And I don't believe that changes if, say, Cornerstone winds up replacing it in a lot of instances.
And what about Cornerstone? Cornerstone hits the big 3 Unaware walls (Dozo, Clod, and Dirge) for super effective STAB. Clef probably doesn't have enough defense to switch into it. The metal birds are still neutral to Rock BONK. All the water walls are still hit by Grass coverage. Most of the grounds are at least hit neutrally if they aren't outright weak to Grass. Dragons are not usually a switch in for Rock STAB and Gouging Fire is hit harder. I said this before, but I really don't think Cornerstone has more than mostly minor differences.
Again, I'm not against a Wellspring suspect or even a ban. But it's not really on me to prove if it would
"move the needle." In my personal opinion, all the other current borderline threats would result in much larger changes since they don't still have relevant alternate forms left. I'll still take a Wellspring ban if you can get it. But it's not like I could refute a lot of the anti-ban stances that are sure to come up in a suspect. Maybe you could. I don't know.
I still suspect we may have to look at mechanics like Booster Energy since it's gonna be hard to ban any particular mon. But that's another tangent.
after Stealth Rock and 1 fallen ally, as well as 2HKOing 
. Tera Grass powers up Grass Knot, and allows Kingambit to resist 
’s Thunderbolt, Great Tusk’s Headlong Rush, and 
.
