I completely agree with this.. If you have a decent number of troops with gift of chaos that would end up aggravating your opponent.Actually it causes major problems for your opponent. Spawn are S5 with D6 attacks and are a seperate unit. So he has to divide up his attacks to deal with the spawn.
Also you always target the vet sgt, lord, etc. In which case even if it takes 3 turns when it's successful it pays off big.