Thariel, the Umbral Wraith Telegraphing...

Just did a Riverhold map where "Thariel, the Umbral Wraith" was the boss. Did I miss something or is this boss not in the campaign?

Anyways, the telegraphing of attacks is non existent, which causes me to die almost instantly because I got no clue what is going on.

Did this escape 0.4 internal testing?