Hey guys,
Just did it recently, it was quite a fun quest!
I do think that there could be some sort of an additional XP provided for completing the 'bonus/optional' part.
As it stands now - for the whole quest including the optional part, a level 8 character (no multi-classing penalty) receives maybe 100 xp for 'kills' and 62 XP for closing the Q.
I think even extremely easy and quick quests such as "Trolls" give more.than this (and you can actually see them being 'spammed' most often, too).
Just a thought!