Apologies in advance for the long rambling that will follow. My opinion literally changed 3-4 times while composing this, so some things might be repeated and it's a bit longer than I intended. But I put 5 minutes into actually building a team, so I feel like I should state my thoughts.
So I tried building a stall team that didn't care about Hail stall. Despite having two Eviolite Pokemon on the team, I didn't really struggle with the residual damage. In one case, I was trying to deal with a SubRoost Moltres and I was happy that extra 6.25% was forcing him to Roost more often. That said, half my team is essentially a free Walrein switch-in. But I did have multiple ways of bypassing the Subs. Perish Song Misdreavus, Roar Steelix, Taunt Qwilfish. I had Heal Bell Clefable to heal Toxic if it arose although nobody really hated Toxic Spikes. Not to mention HP Fighting Cryo and Defensive Escavalier capable of breaking the Subs, but basically to outstall Walrein if needed. The problem with my "counters" though, is that all of the solutions are temporary. There's nothing stopping Walrein from switching out and coming back in. And with his bulk and Ice Body, he's an absolute pain to actually kill unless I can keep TSpikes down or I get him last mon with Misdreavus (or PP Stall, but that's more a reason to ban him than not).
The biggest thing about Walrein is the fact that on an offensive team, if one Pokemon is weak to Walrein, the whole team is weak to him, since the ways to deal with it only stall the problem, which is generally bad for offense. That said, as long as you keep a Poison-type or Rapid Spinner alive, it will be hard for Walrein to get more than 2 kills. But this is where the arguments for residual damage really come in handy, once Walrein sets up. It will kill anything with a Life Orb, Choice Item (except maybe TrickScarf), Eviolite, or Focus Sash, since the Sub blocks status, the less reliable recovery. This isn't like the other annoying strategies where you can hax your way out of it via crits or hitting through confusion, you have to continually switch and occasionally recover with Wish/Roost and the like to come out in remotely decent shape. When looking for a metagame that's fun to play, PP Stall shouldn't be the main answer.
Looking at the next suggested ban above Walrein, the Ice Body+Snow Warning ban, I would 100% prefer this to pure Snow Warning. I always would like to allow as many unbroken strategies as possible, and I personally think just Frotom+Jynx is fine. As a bonus, the complex ban doesn't actually ban anything. Since it's been said that Hail stall usually beats Hail offense, this would allow things like Walrein and Glaceon to stick around and check the remaining Hail teams.
Looking at Walrein's immediate replacement, fully invested Dewgong has more special bulk than either side of the current Walrein spread does (Walrein can have more with full investment though). If Walrein is broken, Dewgong's does deserve looking at for the increased amount of special attackers it can take. Being weaker to physical attackers does have its issues, but the issue of "if one Pokemon's weak to Walrein, then the team's weak to Walrein" can apply to Dewgong as well, since it can stall just as well against weaker special attacks.
As for the faster Ice Body users, the speed can certainly make up for the loss in bulk. To set up on a faster Pokemon, you have to take 2 hits and have over 25% left, but you do get a turn of Ice Body/Lefties recovery. So a faster Pokemon has to deal at least 43.75% to reliably prevent the sub. However, if you set up on something slower, you have to do at least twice as much, or 87.5%. So that extra speed doubles the amount of damage you can take before stalling. It can obviously be less if you manage to keep hazards up, but it can be more if they predict you staying in and Protects rather than sub. I'll admit I haven't tried these guys yet (I laddered with a stall team and I think reached my limit of not doing anything), but theoretically they can set up almost as easily as their more defensive brethren. Of course, I don't want a ban based on theory, so it might be more practical to ban the things we figure are broken, like Walrein and maybe Glaceon.
We shouldn't automatically shy away from a complex ban because we have precedent of doing so with Drizzle+Swift Swim in OU and even SmashPass here. The idea of Ice Body+Snow Warning is to only ban broken strategies. If you really hate the idea, we could consider an Ice Body ban and send Glaceon to BL2. I'm hesitant to straight up band Snow Warning because I don't see it being broken after taking away its strongest component. My only worry about the complex ban is that we're really only saving Snover, Frotom, and maybe Jynx. While I would like to allow as many strategies to flourish in the tier (which includes as much of Hail as possible), I don't want to do it to allow a few specific Pokemon to retain their function in the tier. I'd rather avoid a Sand Veil-esque ban, since I do agree with the reasoning with Evasion Clause and all, I don't agree with using it to bring Garchomp back. This works both ways, I don't want to do the ban just to keep Walrein in RU (albeit less effective) or just to keep Frotom in RU (while remaining effective). Since nothing else seems remotely broken, we can ban conservatively, say just Walrein and maybe Glaceon to start, and then reevaluate whether or not all of Hail gets the boot (btw, I'd rather ban Snover than just Snow Warning).
tl;dr If someone can show Frotom+Jynx is broken (which as Pocket said hasn't been shown definitively), then I'll support pure Snow Warning ban. I can support the complex ban at the moment, since it doesn't actually ban anything, and maybe bans a broken strategy, but if we wanted to start with Walrein and reevaluate the lesser-used Pokemon later, then I'd prefer that. At least ban Walrein, because the things you can do to break it's stalling streak don't stop him from trying again.
EDIT: Of course I just missed the conversation about the runoff while writing my monster post. That would be a good idea.
