Because some monsters are super high defence for certain attacks, and super low for others, so it kills them quicker = quicker dungeons = more per hour = more XP.
I get 14k xp per hour, I'm lvl 77 dung and you know my stats. I tryied your options once, but when I switched it to your options my XP per hour decreased to 6-7k XP per hour.
So I tagged it back up.
: \ I think my iDung isn't a good one lol. I bought it though -
Anyways I just want chaotic rapier + maul. That's all I ask.