Hail teams seem good on paper because ice STABs seem really good against all the dragons that run rampant in the format. However, Ice as a type is not very good in any format, and Ubers is no different. If you look down the list of pokemon that are commonly used in Ubers, a lot of common things can counter hail users. Opposing weather users shut down hail entirely; Dialga and Palkia take neutral damage from hail and can hit back with Flamethrower, Aura Sphere, etc.; Mewtwo outspeeds everything hail has, doesn't get hit by Ice Shard for any significant damage if it runs defense EVs, and sweeps with Aura Sphere (Shadow Ball for Froslass); Darkrai outspeeds and sleeps everything; Jirachi Flinchhaxes everything with Iron Head; Scizor is by far the biggest threat since he can kill everything he sees on a hail team; and don't get me started on what Arceus can do. Ice Shard hurts dragons in general a lot, but without attack investment it won't OHKO anything unless it's used by Mamoswine. Meanwhile, all your pokemon lose 1/4 of their health minimum by switching in, making it difficult to keep them alive if you don't OHKO them.
I understand the appeal of using a hail team in Ubers, but the fact is that other weather teams are just plain better. The two main weather users in Ubers are a physical attacking beast who also serves as an amazing tank and a pokemon with great typing who has the most powerful STAB in the game at full health. Compared to Groudon and Kyogre, and even Tyranitar to a lesser extent, Abomasnow is a slow, frail pokemon and although he has access to subseed, decent attacking stats, and good stabs, he's just plain outclassed. Mamoswine is similar in that, Brightpowder or no, he just can't function that well in his main role as a revenge killer in this metagame.
Honchkrow could be pretty decent though. His movepool is slightly lacking, as he doesn't really have any way to deal with Groudon, Kyogre, Rayquaza, Palkia, and Garchomp, but he can hit just about everything else in the metagame for good damage. A LO Subroost set would probably be the best option, as you can avoid damaging moves with Sucker Punch while still maintaining a relatively good power and coverage (Sucker Punch and Superpower technically gives perfect coverage). The danger with relying on Sucker Punch as your only STAB though is that you leave yourself open to get set up on by pokemon like Mewtwo and Giratina, who resist Superpower. There's also the issue of Scizor who can tear through your paper thin defenses while you can't retaliate with anything effective besides Heat Wave. Heck, using any attack besides Sucker Punch is risky with Honchkrow since his speed is so lackluster for Ubers. A Honchkrow set could work in Ubers, but you'd need to be very careful and it would require a lot of support.
