Froslass was broken in old-UU. Near the end, old-UU was broken-- but no one complained because we knew we were doing the "BL Release" soon.
Old-UU was far from balanced and the defensive-support pokemon dominated the tier. You'll notice the discrepancy in that while previously "standard sweepers" have dropped harshly, old-UU's bog-standard defensive-support pokemon (Clefable, Steelix, Claydol, Froslass etc) are still easily in the top of UU. Goes to show how out-classed sweepers were in the old game, and froslass and rotom were free to keep spikes up for nearly the whole freaking game.
Even with the sweepers being greatly improved, Froslass' mechanics-- 110 speed, ghost typing, spikes, makes it incredibly hard to prevent it from setting up in a metagame with no ttar/STAB bullet punch users. Heh, if anything maybe experience will lend people incentive to try froslass out in OU.
One thing is for sure, hail is going to have a hard time running snover and no froslass. In all honesty, with all the viable taunt/phaze/encore users there are in UU, I do not see walrein as a particularly big threat. Glaceon is a bitch but, it should be managable-- especially if one does not have to deal with 2-3 layers of spikes at the same time. Between Glaceon and Walrein, combined with a number of potential Ice/Water types to abuse Blizzards, the team could still be viable. Obviously, it will be a lot more challenging now.
While I prefer offensive-teams, I think I just might have to try an all-out stall one this round, see if the remaining sweepers can handle a team like Nidoqueen/Registeel/Milotic/Spiritomb/Roserade/Chansey, or whatever. While there are some definite offensive powerhouses, I'll be curious to see if they can keep the game in balance. I mean, Magmortar could rip that hypothetical team to shreds if you predicted well-- but then Magmortar could rip apart almost any OU stall team if you predicted well so it's not like that's easily done.