-If Klingons are stronger than humans shouldn't genetic augmentation only be able to even the odds not make them ridiculously stronger?-
Klingons aren't twice as strong as humans, so augments are stronger. They also have more endurance, better sight, and smarter brains. That is how that group of augments were able to come up with a plan to steal a ship and stopped its Klingon crew.
In the augments first appearance they fight in hand to hand combat with the crew and are able to beat the Klingons in moments. One augment kicks a Klingon at least 6 feet across the corridor yet we do not see this happen when they fight humans.
When a hoard of Klingons board DS9 with superior numbers, we see Sisko, Dax, Kira, Dukat, and Garak fend of the attack (each taking out multiple Klingons); with no casualties and only one severe injury. That doesn't speak well to the superiority of Kliongons over Humans.
Klingons, Vulcans and numerous other species are supposed to stronger than humans.