[Guide] Top Metagame Threats

[Dragonstrike]

Asking in friendly and curious way since my practical experience in competitive metagame dwells somewhere between 0 and 1, but goes the banhammer on Snow Cloak and Sand Veil as well?

Saying, my Glaceon holding an Icy Rock forces a hail with the same-called move, which boosts its evasion thanks to the ability Snow Cloak. Using the move Barrier it beginns raising its Defense while giving constant damage to the opponent if they aren't protected from the weather condition, then sweeping with Blizzard, which has a accuracy of 100% during hail. How big is the luck-based aspect in that case?

Snow Cloak and Sand Veil give a 20% evasion boost, and it stacks with other evasion sources (such as stat buffs [chance to dodge increases a lot as the stat boosts accumulate] or items like bright powder [a 10% evasion boost]) if used like that.  It's not as broken as when weather wars were a thing in gen 5 of the series, but it's still fairly significant due to that stacking.

Evasion ability plus evasion stacking plus decent bulk = the ban hammer from Smogon.  Don't ban evasion in general, and you'll see sets like that often, dragging out battles in a luck based evasion war.  Heck, even Bright Powder by itself is banned, because it's a luck based complete negation of damage.