Graul

Execute doesn't scale *much at all*, your other instants and melee attacks do. Execute only makes up 5% - 8% of my overall damage ever depending on the length of the fight. For your gear level 10% - 12% seems about right. It also looks like you were either having rage or threat issues due to the low amount of Heroic Strikes. Having either a Feral Druid or Ret Paladin in place of a 3rd Rogue in that group would work wonders too, but I know some guilds prefer to run three Rogues and want them all in the same group.