Haha, Im glad people are comming fourth and admitting they were tricked by the silly Sheogorath!
One reason it took so long for me is because close to first getting to the arena, (which btw there is already an arena in the game...Arena mod anyone?) I shot the middle guy on the platform and it didnt do anything, so I figured, oh, thats obviously not right...So I continued shooting the Antronachs and was getting pretty annoyed and just randomly shot the dude on the right and, voila! lol. But yea, I guess I should have known..Being Sheogorath and all...
I had no idea what I was supposed to be doing, so I was sneaking all the way to that arena and when I finally got there one of them must have already died. There was just one standing there which I shot a few times and then started pegging the guys in armor.
I ended up having to restart because a dragon decided to attack me while doing my third part of the quest and the wabbajack didnt harm it.
Ha! That definately sounds like quite the bug! Did you have patch 1.2 at the time I wonder? lol
After I realized that the Frost and Fire atronachs were doing barely any damage to each other, I got bored and shot everything else. I'm not clever; I'm easily distracted.
Thats kinda how it happened for me, except replace bored with angered..lol
p.s. Isnt the Wabbajack great fun! Ive always enjoyed using it! lol