It seems like monsters do not cast spells. Wished for kobold shamans and liches run around you trying to hit you, Guth'alak does nothing.
In previous versions Guth'alak attacked you right away with magic missile and confusion.
Happens to me both in exploration mode and normal mode (easy to test with Guth'alak).
I just rolled a random char in R69, went to the village and kicked the druid.
B, the trollish fighter, was blasted with magic missiles by Guth'Alak, the druid.
EDIT: Sorry, I just noticed this report is for R73, not R69.