This is something new in patch 5, and it was implemented to stop an exploit where if you used Darkness, or Fog Cloud on a vendor they would stay in it and let you steal everything from them without penalty. So now NPC's will try to run out of it which makes sense.
I see, I never used the spell before patch 5. I guess they had to address the exploit in some way. Thinking What the use of the spell is now. Getting enemies move from certain position by making them run outside the spell area works fine. Creating an area between you and the enemy so that they can't cast spells or shoot at you, hm, you can't to that to them either. Use it to sneak by npcs/enemies? Yeah, possibly.
But you are saying used in combat they won't engage you in melee in the Darkness spell, or they run out of it? Honestly that sort of makes sense. Although yeah, there should be a chance of falling off a cliff blind. Wonder if that would be hard to implement.
I was ok with them not being able to engage me in melee as blinded enemy simply can't do that, but since they dash out of the dark area (as if they actually saw which way to go) I can't engage them either and that bothers me. Why having
Devil's Sight when there's no one in the dark area except you? There's nothing to see.
I'm ok with the ranged warlock build actually I just wanted to try the melee build i heard about.