I need help with my stat math.

[Pells]

So I did the math for tenacity and direct hit. This is what I found out. Please tell me where my method is wrong. My raid group is freaking out that I might meld tenacity.

The setup:
Right now I can max tenacity for 6.5% more damage or max direct hit for 13% chance to do 25% more.
100 swings for 100 damage and that equals 10000 damage
So out of 100 swings 13 should be direct hit. 25 damage per which is a gain of 325.
For tenacity it is 6.5% to 10000 which is 650.

Am I missing a factor here? Please don't post about scaling. I know that and agree. This is the stats put into actual swings.

The math works out.

I've heard wildly varying numbers on the % gain of Tenacity though. 6.5% is one of the higher claims.