I just ran into this issue as well. I fight the werewolf and get him to zero health, then he walks to the cliff and roars infinitely. His empty health bar remains at the top of the screen regardless of where I go. I tried fast traveling away even, but that doesn't work.
I was really interested in the outcome of this quest
System:
ASUS Maximus VII Hero
i7 4790K OC @4.5GHz
SLI GTX-780's OC'd @1150MHz
16GB DDR3 @2400MHz
Non-DRM version 1.11, Installed on Corsair LX 500GB SSD
Windows 8.1
Ok i've tried and IT WORKS! On the last version of the game even if the bug was already "begun" i could complete it with no problem!
Thanks CD Project
(version PS4)