I don't like suggestions like this because it risks some of the more challenging (and dare I say enjoyable) content in the game getting nerfed. I do agree that some of these fights are made more difficult depending on your class. For me (Succ Musa), I'm not supposed to Float/Knockback the last boss during the PEN insignia daily too much out of her Forward Guard or else she does her massive AOE. I have to make sure I use only specific skills to chip away Khaoraxias health before I just DPS her down.

Devise the strategy you need to complete it, it will be different for everyone.

For your example with Kauha, I've found that patience and proper positioning matter the most. This is not meant to be a face roll game mode, and neither will boss rush.

OP, which class are you on that you are having so much trouble?

It doesn't have to be RNG. Get the HP of the sword shield one down to like 30% while also killing the big axes one in the process since it dies much easier, then the big axes one respawns and you can kill both together. Do the same thing when 2 of each spawn in the later phase.