Yeah, I was asleep, but basically the only thing you need to hit with that slot is Azumarill, so hitting Whimsicott is just a bonus, considering it has higher usage than Empoleon. Whimsicott troubles rain teams too actually, as it resists the stabs of Kingdra and Ludicolo and Seismitoad, leaving you with Kabutops Stone Edge which I doubt KOes a physically defensive spread, not that it matters considering Whimsicott just spreads paralysis, making rain difficult to abuse. Most rain teams don't run Tornadus-T anyway now, but even then it wouldn't like to be paralyzed. It's definitely relevant enough to mention when Empoleon is easily taken down by Seismitoad / Kabutops with Low Kick / any Thunder abuser.