Just did this quest. At the end of the battle on the lighthouse roof top, joxo started attacking me (and doing damage even though I couldn't fight back and he was still coloured green). I stopped this by running down the stairs and back up again, but then there was no question mark to indicate that I was meant to talk to him again.
Not sure if it was a bug, but the first round of the battle (on the Island) as a challenge. The first battle lasted about 6 minutes, with his hit points hovering between 11,000-12,000 for the last few minutes of that. I was doing this as a level 33 mage, and about 90% of my attacks were being evaded with the rest just glancing. I gave up at this point and left the temple. I went back in and tried again (since I couldn't leave the island) and this one lasted just under 5 minutes (my void elemental timed out within a few seconds of winning that fight). It is possible that my stats were too weak, but I thought I should flag the extreme abundance of evades just in case it is not intentional.

