Weapon Augs are really weird. They have inconsistent effects. Like, they suck on certain weapons, but then excel on others.
I crafted a Carnifex with the sticky grenade aug, and it was crap. It barely did any damage. But now I crafted an N7 Valkyrie AR with the sticky grenade aug, and this thing is insanely good.
its almost like every aug is meant to be used with a very specific weapon for best results.