My memory is a bit poor but can anyone answer this question for me?

[Shadow Archon]

A headache.

Aside from the Sarcasim, Yes, I agree with the Psi Disruptor thing.

[Visions of Khas]

I agree that reincarnation isn't instantaneous, but likely takes some time. Game mechanic.

The only instance where this is referred to outside the game is when Fenix leads the charge on the Cerebrate in The Fall. He monitored the brood for two hours before reporting back to Aldaris that the cerebrate was regenerated.

[Shadow Archon]

It could of just been the Second Overmind capable of instant regen of Cerebrates.