Blood Weapon / other DRK suggestions:

[Chronons]

snip

Ah, I see one reason why our numbers may differ. I forgot enhanced FoF means 60secs of uptime in a 3 min interval. Thx for pointing that out. But, i'm still not understanding your math process.

DRK: 1x.8(Grit)=.8 [(.8x.15)+.8]Darkside=.92 <- here we agree
PLD: 1x.85(ShO)=.85 [(.85x.3)+.85]FoF=1.105
In a three minute interval DRK. will be a constant .92, PLD will be at 1.105 for 60secs and .85 for 120secs.
An average for PLD over that period would be [(1.105+.85+.85)/3]= .935
That being said, the fact that DRK has higher potential damage means it will still do more while in tanking stance. There is no way the 1.5% difference in the averages is enough to compensate PLDs lower potential dps. The only parsing data online I can find has PLD 50-60 dps lower than DRK, much more than a 1.5% difference.