I’m making sure I walk next to every enemy I can to slow them with shadow power, but it isn’t registering any of them as slowed for the set dungeon quest and the counter remains at 45. Furthermore, though I have no follower and am using impale to kill enemies, it is randomly saying I have started the chain and lost the chain regardless of whether or not I am impaling at that moment the notification is up or was seconds ago and DID hit enemies with every dagger I threw. I don’t know wtf is going on, I’ve dismissed my follower and upped the difficulty repeatedly to make hitting enemies more regularly easier, but still the impale chains pop up and break themselves regardless of whether I’ve cast and hit someone with the ability or not and it never counts the enemies I slow with shadow power for the set objective progress.
Not a bug. You have to activate Shadow Power when you are near them. The Night Bane rune only works when you activate the skill. It is not constant.
Also not a bug. Look at your quiver.
As TimberWolf said, this is not a bug.
See if this video helps. It’s less than 4 minutes long and tells you all you need to know:
Before posting your next “bug” try your browser’s search engine first. There’s a lot of good information out there. 
need I remind you the set uses all runes for shadow power and makes it so that once activated it is ALWAYS ON.
Pay attention to the wording of the rune…
Night Bane
Slow the movement speed of enemies within 30 yards by 80% for 5 seconds.
So, if you enter the dungeon, and press Shadow Power it will indeed remain active from that point on and the duration of the dungeon. However, the slowing effect would only occur on mobs within 30 yards when you initially cast it and last for 5 seconds. From that point on, unless you re-cast Shadow Power, you won’t cause any more mobs to be slowed, which is what the set dungeon requires.
This is not a bug.
You don’t have to remind me because, unlike you, I actually know how that skill and its runes work. That is why you cannot complete that set dungeon and I’m able to routinely master it. But yeah, just keep making stupid mistakes and refuse the learn. That will show … someone.
This forum is responded to almost exclusively by fellow players trying to be helpful. You reported something as a bug which isn’t a bug. It was explained to you why it’s not a bug and you were given advice on how to master the set dungeon successfully. Please don’t make people regret being helpful by insulting them for providing the help and advice.