Im going to have to agree with Dittocrow, hail doesnt look broken to me at the moment, sure its a pretty cool playstyle that brings some powerful options to the table, but it suffers from some crippling flaws, most notable of which is having to run a mediocre pokemon for the playstyle to work at all (mediocre, not useles, sash snover is a cool little dude). Hail also struggles with the fact that you often have to stack up on Ice-types like Rotom-F and Glaceon, which while powerful, are burdened with weaknesses to common moves such as fire blast, stealth rock, drain punch, close combat, and iron head. Thanks to these common weaknesses hail teams often struggle with common Pokemon such as Durant, Escavalier, Entei, Emboar, and Gallade (SubBU can actually beat many common hail cores by itself), who can break through the hail abusers with little trouble. Slowking is a great choice for a bulky pivot on hail teams, and helps to alleviate the problems that ice types have with its resistances to fire, fighting, and steel, as well as its ability to hit Rock-types sure effectively, and imo slowking is a requirement on any hail team because of this. My current verdict on hail is this: hail may be a cool and somewhat powerful playstyle, but suffers from crippling flaws that prevent it from performing to its full potential, and therefore should stay in the tier.
Sorry if this post makes little to no sense, i woke up really early this morning and im quite tired x_x, so please bear with me.