By accident, just a few days ago I've also filled in
a report about the same quest.
I've tried to do this quest on two toons on the same day - for the first one it worked smoothly, for the second - there was the cut scene but no Morrok to hand in the quest, just as you describe. It's ok that the "moving" Morrok disappears, but at the same place a "static" Morrok with a yellow "V" should have appeared.
I've tried 8 or 10 times to drop the quest and try again. I've changed channels, logged out, died, tried to do this in pt and alone. Nothing. So I have filled in the bug report.
BUT I knew it worked on the same day on another toon so I didn't completely give up - whenever I had a chance I tried again and again and ... at some point Morrok has appeared!

Half buried in the ground, but enough to hand-in the quest. I believe this was about the 16th attempt altogether...
So my tip is - don't give up. Try restarting the client, maybe even rebooting, do your plusing-dance sequence, hold your ear and nose with two fingers of the same hand and then try - but don't give up, eventually it will work.
And to the team:
here is an older example of someone listing Surprise Attack as one of bugged Morrok quests: so the problem is not new and imho should be reported. It's just that it's pretty random - as I said, for me on another toon everything worked really smoothly on the same day.