They didn't go seriously in-depth to the effects of the Pax gas in the movie, but one could conjecture that if the "normal" effect was to make people lose the will to do anything (including work, mate, or eat), the "opposite" effect would be to make them hyperproductive. And crazy like foxes in terms of tactics.

(The fact that everyone is freakin' terrified of them also probably helps their ability to win fights, as well.)