Aard Dagur actually sounds neat.
The only decision I am unsure about would be Regis, has he worked out for you ?
I am still somewhat under the impression that (unless you run Eithne) Regis would be somewhat unreliable and uncontrolable.
Your list looks somewhat more like a Bran deck, than an Arnjolf deck though.
Your list actually appears to be a lot of fun to pilot, though I wonder why you do not run Champion's Charge.
Arnjolf's ability actually makes Regis quite easy to pull off; Aard is in there to line up more units if needed. Those 2 cards play quite nicely together. Nivellen is the obvious alternative but you'd be missing out on damage that Aard provides to better coordinate the Regis sweep.
It's a trickier list to pilot because you'll be tempted to keep all your key cards (ie Dagur, Regis, Aard) for the big combo at the end. At times, it's better to go aggressive round 1 by throwing Dagur down and getting some damage in with Ocvist & Delirium. It really depends on what kind of hand you're starting out with.
Ideally you want to keep the Trophy Catches for Coral but sometimes it's better to use them on a momentum swinging, row dependent card (Corvo & Avallach come to mind).
Champion's Charge might be worth teching in over Djenge given the prominence of MO. Good suggestion there. I wouldn't swap it out for Ulfheddin because the deck needs those damage on deploy cards to trigger the bloodthirst units.