Hum, not sure.  I'll keep a look out to see if it's happening. 

This is related to another issue that's plagued the beta for quite a while. It mostly happens under 2 conditions:

1) Your target is just slightly outside the ability range. He will stand still. If it's far enough outside he will move to get in range, if it's within range he will just do it. There's a "sweet spot" right outside the radius circle where he'll ignore the command.

2) He's inside the hitbox of another Demigod. Rook is the biggest offender. If he gets lost right beneath the Rook's feet, the ability won't be used, you'd have to move him out and then do it again.

This isn't Erebus specific, but is mostly noticeable to melee Demigods since a lot of their abilities are fairly short range.

This I haven't seen, and I've been playing him in the SP Tourney.

I generally ignore Erebus' minions and don't invest many points into them, so I'm not very aware of their actions. However, the few times I have used the minion build, I have noticed that they often times switch targets before killing the intended target. Guess I'll just have to live with the few pathing issues and hit-box/proximity problems for a while longer. I just assumed enough people had complained about these in the beta that it would have been fixed by now. I must say though, balance right now is much better than in beta... I can actually do some major damage with Erebus and not just play teleport/stun support all the time  

You have to make sure that you're selecting the minions, too. Any new minions don't join the existing selection, so you have to periodically re-select as your existing minions die and new ones are created. I haven't seen any of my selected Nightwalkers switching targets randomly.

doesnt always trigger, its ver frustrating...

i guess its prob a good thing that this game is taking another month to be released here, coz maybe theyll be able to fix many other minor bugs and patch em up b4 i buy the game