Syndicate Safehouse fortification boss is immortal

Hi,
I just invaded fortification safehouse for the first time. I got to the arena part where i encountered Tora the Culler and dpsed her to 0 hp in a few seconds but she is still living and atacking. I tried to leave the instance i even was waiting for 10 min to proc her hp regeneration but after that she was still immortal.

SAME HERE 2 TIMES IN A ROW I THOUGHT THIS WAS THE POINT OF THE LEAGUE? iM GETTING VERY FRUSTRATED!!!! MIGHT AS WELL QUIT TILL ITS FIXED OR DONT ATTEMPT SAFEHOUSES.