Definitely Fire Knight, considering all of his attacks are multi-hitters, plus the speed reduction and TM reduction. He also has potential for Clan Boss once you get his masteries done, he'll get loads of Giant Slayer procs, plus some poison. And he would certainly be usable in other dungeons, though not exceptional and likely to be replaced at some point.
Definitely Fire Knight, considering all of his attacks are multi-hitters, plus the speed reduction and TM reduction. He also has potential for Clan Boss once you get his masteries done, he'll get loads of Giant Slayer procs, plus some poison. And he would certainly be usable in other dungeons, though not exceptional and likely to be replaced at some point.
It'll be interesting to see his multipliers on that A3. If they are pretty high and then you have the 10% per poison debuff... it could be interesting.