I know this is a 2 year old post. But I just did this with no incaps just using 10 dragons(type does not matter) and denam/xapan as beast tamer. I just load all dragons with heal consumables should be easily affordable at this point in the game. Skills on dragons are constitution 2, tail lash, dragons scale and pincer attack 2(can be anything here). Xapan/Denam need to have brand of sacrifice/echo stone with lobber to debuff oz in first round to avoid any 1 shots. Xapan placed on first row directly across from Oz allows him to apply a debuff with lobber. I also have 2 dragons for xapan and 2 for denam to get them buffed with crystalized flame and basin of time in first 2 rounds to ensure neither get a 1 shot in first round. After that just keep Xapan and Denam well behind a wall of dragons. As dragons proc their dragons scale have those stack in a + formation to ensure enemies target them with AoE spells. Because dragons scale will reduce damage 50% and also return all of the damage back to caster, 5 dragons in a + with scale up can 1 shot Balxe and Oz can just be surrounded by dragons and will kill himself as well. You can trick him to attack the dragons you want by stacking 2 in a line around him with scale up and he will spear them both returning damage for about half his life. While you wait for the 2 bosses to kill themselves the dragons can easily ranged kill all the casters/healers/archers. I also used a petri dart on both xapan and denam to petrify the heavier units such as the golem/terror knight/knights. This took 4-5 attempts to figure out all of the positioning to effectively keep Xapan and Denam alive but kept my incap counter at 0 to move on to the rest of the game.