The Black Sacrament -- A Guide To Black Mage

What does a modern Khatvanga Occult Acumen nuking set look like?

There hasn't been any new occult omen gear, so exactly the same as it has been, no?

Khatvanga is a very poor nuking staff compared to other options. I'd bet Mpaca's Staff out-nukes it and has refresh+2 on top as well.

Use club/shield and moonlight. Need more mp, switch to staff and AF coat, cast one impact in an OA set -> Myrkr -> back to club/shield.

AF coat won't ever give you back more MP than the cost of the spell. It cannot be used to entirely refill MP.

Most gearswaps have a setup for auto-using AF coat when MP is under some threshold, usually 40-30%. The same setup can be used to auto-swap to staff on that same threshold if you want.

Then it's just nuke as normal, when you see yourself in a staff wait for TP and use Myrkr to get back to full MP.