Since my Rogue is kind of in cruise control in Suramar now working its way towards Pathfinder I've decided to mess around with a Death Knight on the side since it's the last class I haven't really tried. It's a lot of fun, feels like some weird grimdark Paladin mashed up with a Warrior. All of the specs seem interesting but I've enjoyed being a low budget Arthas the most.
Follower AI is probably the same shit sandwich driving Warlock and Hunter pet A.I. There's all sorts of weird pathing and behaviour issues in Legion, like the one you just mentioned. It's why I just leave all of my followers for missions instead of using one as a bodyguard.
What's the issue with the DH follower Belath? I've seen him run away and keep far away while I'm fighting stuff more than once, or only hit a few times when he stays close (not always, but enough to make me wonder). Is this asshole in reality a KJ spy trying to let me die, or just some busted A.I.?