OK,

There have been many arguments about if and how augments stack. I got tired of all the forum posts about that crap so i decided an experiment was in order.

Two augments i know work together and do completely stack are the Luck and life, Luck and skill augments. I ran through bandit coast testing them individually and together as well as just my little master cutlass by itself. Both stack together. Realizing that i was one-flourishing all the bandits (Including highwayman ambushes) with the two augments in bandit coast, i took a trip to wraithmarsh. With the same augmented cutlass i took down a banshee with exactly two hits, half health a hit. i later encountered another banshee and decided to add a positively charged augment to it knowing that the lighting isn't specifically strong against them. I took a little over half health with one strike, when i took the other banshee down to exactly half heath, with one strike, without the positively charged augment. So just to make sure i saw it correctly i loaded wraithmarsh again this time using the third augment first on the first banshee and no positively charged augment on the second and it does in fact stack the positively charged augment. I reloaded back into wraithmarsh once again to test the final augment i' wanted to test and that is the mighty oak augment. The mighty oak augment did not stack. I started playing a little bit with combos of the augments in the dlc for knothole that had no side effects like flames gift and came up with the same result. I think that personally, there might be a cap on the damage or extra damage a weapon can do. My guess is x3 in extra augment damage.

..................I think they want you to figure out better combos than just rape weapon.

I hope this helps you guys. I know i got irritated looking for the same answer with no consistent truth.