Yesterday I got the Heroic Horrifying Horn Arbalest off of Zon'ozz. It's a item level 410 weapon with over one thouuuussand base damage per second. My current bow from Normal Madness is only 939 base damage per second. So I do a little happy-dance, slap on a woodchucker scope, and transmorg it into a gun.
Then something gives a little tug at the back of my mind. "Is it actually better?"
I hit up femaledwarf.com and plug in everything revert the weapon and... it looks to make my dps better by 0.081%. Yes. Notice the decimal point? That's not even one-tenth of one percent better. And this is of course factoring in all the perfect buffs and debuffs. Without that perfection the margin would be even smaller. It is also not taking any movement into account. At all. With the movement the proc DoT from the Madness of Deathwing bow will tick while I move. The higher item level crossbow will not do much. So if Zeherah's summary modeling of the proc is good, then the Madness bow is better.