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I'd argue that the ddance set should have an option to run naughty nature, replace steel wing with fire blast, and put 4 evs into the special attack stat to achieve perfect coverage in the current ou metagame.
I find it hard to believe that weavile isn't even B- rank. It is the perfect partner for dragon spam teams, and if you are rocking a dragon slower than latios you can rely on weavile to decimate the latis. Weavile can also handle lando and ferrothorn who drop to life orb ice shard if it's...
It has all the coverage moves it could ever need besides ice punch. It has 4 set up moves and grass, fighting, ice, fire, dragon, dark, and electric coverage
Due to it's frailty any se priority move should knock it right out. Also thanks to it's lackluster hp and defense stats it's easily worn down so just use something like mega pinsir or mega lop with dual priority to wear it down. You can also just run a hazard stacking team.
Every single dragon type you would argue as ridiculous was answered easily during gen 5. For instance salamence, dragonite, and garchomp were easy to ohko thanks to mamoswine and weavile. Hydreigon was cut down quickly thanks to it's lackluster speed as well as it's 4 common weaknesses so...
It is forced to run steel moves to cover it's new 4x weakness, and had it's coverage moves and it's most powerful stab move's bp cut. It was very clearly a nerf.
Hydreigon had no reliable switch ins besides physically defensive chansey in gen 5. It was an amazing pokemon that was harshly nerfed in gen 6 thanks to GF's ignorance.