*Disclaimer* Everything here is simply an opinion and not a suggestion or fact or anything solid. Take it with a grain of sugar (because salt is salty)
I'm not sure how well it would hold up in league, since there won't be much momentum to your team (putting U-turn on Clawzitzer and Noivern MIGHT help), so you'll have to really hope that your stalling holds up well. You don't have a team that makes pulling off a sweep possible, unless you get really lucky. Sure, your Clawitzer will be a bit tankier than usual, but it's speed will guarantee it goes down after 2-3 hits instead of 1-2, and without specs of life orb, I don't think Noivern will pack enough punch (especially with timid nature). Mamoswine is a solid member, but it has a fair few weaknesses, so it will really depend on matchings as to whether it does much. So with a sweep out of the question, your main hope will lie in your stalling ability and managing to play around your opponent. Thankfully, you have great stallers (not too sure about no hp EVs on Tentacruel though, that might be a problem), but I would definitely get whirlwind on Skarmory for phazing, especially with those speed EVs.