>>96247683
I always got the impression the Sisters were deployed more as a propaganda tool and for objectives of significant cultural or religious value, rather than actual combat efficacy.
Like, the guard are there being all hammer of the emperor and feeding millions into the grinder of a 10 year trench campaign, then the sisters stop by for 3 months as a stalemate is broken and their campagin is essentially them fucking up the depleted enemy with their fresh, zealous forces that re-invigorate the schlubs who were all starting to seriously consider feeding their commissar a krak grenade for breakfast