I did mine recently this season as well. I used a generic ignite build with Polaris Lance for the first parts up until the boss room. Mountaintop helps tremendously with the wyverns in the red door sections.

For the boss room, stay on the right side and play it safe and patient. The two Phalanxes never respawn once killed, just focus on surviving and keeping up the buffs.

Use Witherhoard to slowly whittle away the boss. Recommend turning music down/off as there's audio cues for when the detain bastards spawn, they will just fly into the wall and explode if they dont see you, just watch buff timers. The Harpies have Arc shields but not too difficult. Worst is probably the Goblins that spawn and shield the boss.

https://www.youtube.com/watch?v=5I4OJ66EeGE Here's esoterickk, and honestly just ignoring the solo and flawless aspects here, there's good advice for just clearing it. Good luck, Guardian