I think the Djinn Arcanomancer is fine as a player controlled creature, but really frustrating as an enemy. I use an artifact enchanted with his ability specifically for sigil fights and circumstances where I feel like I’m likely to encounter a nether enemy, like the “catch the runaway creature” duties. I assumed that this was the creature’s intent when it was designed, as his ability is a wasted slot when you’re not fighting nethers, which, in my game at least, is most of the time.
I’m not a programmer, so I don’t know how difficult it would be to implement this, but I can think of some solutions:
Make the Djinn a special monster that doesn’t appear in the realms, like the Paragons. The cores could be acquired through exalted emblems, arena rewards, or power spells. I think this is the best solution, as his current ability is really unique and does have a place in many builds, at least as an alternate or a swap-in.
If he does continue to appear in the wild, make his ability different when encountered as an enemy. Perhaps increased damage and defense versus nethers instead of completely neutralizing them.
Turn off his ability completely when encountered as an enemy. Boring, but viable.
As it stands right now, the possibility of encountering the Djinn Arcanomancer discourages me from having a party full of nethers, which was what I felt to be the natural endgame progression. I don’t run nethers in my current party anyways (I’m waiting until I have all six made), so I had assumed that his ability simply didn’t work when encountered as an enemy, as his likelihood of appearing (I see him quite often) would completely defeat the purpose of the most difficult part of progression in this game. Based upon this information, I would avoid using nethers until a change was made.
In short, I think the creature is really well designed, but could use a change in implementation. Still having a BLAST with this game though : )