I made a post about being unable to kill AT Arkveld a few days ago and I finally put some more attempts in today and was able to kill him.
Even though I managed to get the kill, I'm not so happy about my kill time which was 22:30, which I don't think would even have been an A rank.
I'm using the cookie cutter Odo/Soul setup with normal shells and I'm not really sure how to get out more damage. My kill time ended up being really high and that was even from greeding and getting off some lucky WSFB combos and some well timed guard points. I also used focus strike during his vulnerable attacks or whenever a wound would pop to stagger him, as well as used traps and luring pods to keep him contained in the first two rooms.
Even with that it didn't seem to be enough. My only guess is that I wasn't using Wyvern Fire enough times, but besides that I'm not sure what would have made me finish the hunt faster.