So I got hit with ranger's Maul, which in the combat log said it has base damage of 511 but it hit for 13034 damage. So that's x25.5 damage (2550%). Even with full might and vuln stack how's that possible?
511 isn't even possible, considering the base damage of the ability is above 700 at level 80. (706 according to wiki)
It has a 1.75 scaling on it so damage is much closer to 2200+ damage. Then add Might and other damage buffs on top and you can easily get a 13k hit.
Personally I've been hit by 25k Maul on my Warrior before and didn't even question it. That's how it be sometimes.