So, mechanics have changed. While leveling a twink I also came by this boss, played as before, got one-shot. Tried a second time, same results. Read this thread. Suceeded. So, they apparently changed the behavior. For better or worse? I don't know and probably don't care. May have been part of the patch-nodes for all I know. Play, fail, check forums/guided, adapt. That's the way the MMPORG world works, isn't it? And a big thanks to all who figure those fights out initially and share their wisdom in forums and guides. May the Force be with you!