Areagne on Cruel?

Just fought her and she seems to constantly spawn in rares. She'll be invulnerable while the rare is up; you kill it and start damaging her and she immediately spawns another one, regains all the health she lost, and becomes invulnerable again.

At one point she wasn't spawning the rares for a bit, but every time I got her health low she would teleport completely across the screen to a dark corner and regain all her health.

Then she restarted spawning the rares and going invulnerable again. Rinse and repeat.

After 5 minutes of this I quit the fight. Is this a known occasional bug? I don't see anything about it with a quick search. The build had no trouble with Napuatzi or Doryani, and I killed Areagne (cruel) with none of these issues on another build.