One thing I learned about game design when I started playing Frozen Throne a long, long time ago: if there's a foe that grants invulnerability, don't let more than one of them exist at the same time, or they'll grant invulnerability to each other.
Now the problem with IA is that there are too many enemies that grant invulnerability to other enemies. In the previous version, we only had firesong druid, which is not hard to deal with. But in U43, lightbringer and brewmaster were added to IA, applying invulnerability hardly or softly to their companions. When there is more than 1 of them it often results in all enemies being invulnerable. At high Arc most of the healing comes from Pale Order, and the consequences of all foes being invulnerable are often disastrous. Sometimes I can kite to unprotect some monsters, but at high Arc, more often I lose my thread before I succeed in doing so.
Please consider improving this before the U44 PTS goes live