I value consistency very highly in my builds, which is why I've usually avoided GWM. I've never done the math, though, so I'd like to thank GM4Him for that. Looking through the numbers, I may be changing my mind soon.
So now the difference between GWM and without it increases even more. 2 attacks at 80% chance doing 5-15 damage versus 2 attacks at 50% chance doing 15-25.
The first setup has an expected damage of 16, while the second deals 20. This doesn't factor in the occasional extra attack or the fact that GWM is opt in.
It's worth another run through. Any news on the next patch?