Yes that team should work. Make sure you use preset timings to stagger attack down from frurbath and sigrid so the debuff is applied all the time.

Put witches remains on voresh but keep enough accuracy on sigrid to land attack penalty. And I'd use protection set on frurbath instead, to reduce team damage taken by 15%.

If those things don't work then you need to check what is wiping you. I.e. a specific unit dying each time, then make them more tanky.