I just want to start off saying that delves are probably my favorite addition to WoW in this expansion… but…
Brann constantly taunts one or several mobs off of me that I’m currently trying to AoE down. I need these MFs to stay in my Death and Decay to be effective, but not only that he runs off with them into the next pack so I cant get to them without pulling even more.
Does anyone find this behavior of his helpful?
Is there a way to turn this off, or has Blizz addressed this in any way?
He’s done that to me when I’ve been looting a chest…
All I heard was “ahm going all in” flats in the air and throws lightning balls everywhere.
I just roll my eyes call him a c*@t and go rescue him!
I would love an option to just complete the delve without Brann.
Brannn Jenkins! 
It’s just a poorly programmed algorithm that was created for Brann. Probably a copy & paste of an existing algorithm that they’ve used for some basic NPCs in the game, like those who attack the mobs in the first opening quest for Legion.
The only way Brann isn’t going to be a pain in the butt, is if they go ahead and completely rewrite the code for Brann, but I really don’t see this happening. So what we see is what we get unfortunately.