Uh, if you could get 2 mod tower and a +2 , -1syou could get 0 s cooldown and 5 dmg
Stacking the -1s mods never drops the cooldown below 1s - I tried that already. If you could, that would instantly break the game regardless of having the +2 damage, because you'd hit for infinite damage even with the baseline of 1. The instant the fight starts, you'd hit for 1 damage, then with no delay, hit again, and again, and again, and again... no matter what HP enemies have, they would die at 0s if you could reduce the cooldown that far.