I've tried him about 3x now and get no information about the fight. Blank. Nothing.
Screen doesn't change; doesn't tell me if I've won or lost (my stats/damage aren't that far off others in this thread). I leave it sit for a minute and then, after a while, hit 'continue fighting' only to be told I'm dead.
It's a known bug, see beow on how to deal for now. Good Luck! BTW, if you're not in a guild, join the Knights of the Round Table.

Lv 21 boss, harder than normal lv 21 npc... so judge it yourself.
I defeated it with a legendary nutcracker and flash
What's a legendary nutcracker and a flash? Do you remember how much you hit with?
Darn thing just killled me and I didn't even see how close it was. The battle never displayed - page just froze. I reloaded and was dead.
The battle page is always bugged. It never show result. Just fight him once, if u die means u fail, if you survive, go and claim your reward and stop waste your time there.