Good job reading the FAQ. Using a spreadsheet would have also worked.
Originally Posted by chalon
The reason Combat benefits more is because you can get Serrated Blades and because Prey on the Weak increases your Rupture crit damage.
It's not going to be enough to make up the ground on a single target murderable fight, though (or something like Iron Council, etc) in the general case. But there's a lot of other factors to consider on a fight and whether or not Mutilate or Combat has an advantage.
Does 7/51/13 outweigh 15/51/5 and 18/51/2 once you have 4pc T8? I haven't seen much on the subject so far, and would seem to affect choices in armor penetration gear, etc.