So with shrouds they'll enjoy the E9 bless. If they enter communion in Skratti form they'll receive 50 fatigue. With 2 slaves as you said - 25.
Only annoyance is wolf form after battle.
I said nothing about equipment b/c its orthogonal to the communion, just equip them however best fits the circumstance or don't equip them at all if that's not required. I'm a minimalist when it comes to managing armies and SCs
The above said I must admit that this is indeed a corner case that may possibly come useful under relief+E9 bless as a last ditch nasty surprise.