It would be nice when they randomly run in any direction, and absolut cool when they even drop down cliffsides or other holes in the way because they are blind.
Running vs a wall and stun themselves. So many options and funny too.
Like good old Slapstick.
I'd absolutely love that

The issue now is that though blinded they take the shortest way out of the spell effect area which doesn't make sense.
Blinded npcs should have no way of knowing the best way out. They should wander helplessly in the dark (maybe find the way out by accident) so they can be taken advantage of whether you are a thief or an assassin or just for the fun.
The only problem i have with Darkness is that its still working like wall for your characters inside ...
So you cannot cast outside when you have devil's eyes eldrich invocation (allowing wich, as i understanded it, is its only reason to its existence). :-/
Yeah, if you have
Devil's Sight which makes you not suffer the
Blindness while standing in it
and there's no any other sight restricting condition you should be able to range attack or cast.