The Three families are probably more lore-worthy warriors than gameplay. I'm sure people would complain if they were going up against the equivalent of Legion veterans after being stripped of their gear.
Lore-wise, the Three Families were able to defeat the Great Khans, who, while not the best warriors in the world, are pretty damn decent. A Great Khan could at least take out an NCR trooper.
Well it may be true that "A" Great Khan can take out "A" NCR trooper with ease, the NCR has displayed on more than one occasion that they use numbers to defeat their enemies. The Khans have already suffered a major defeat vs NCR.
I do not believe any of the 3 families are any better in lore than you see in game. House mkl securitrons, and the three families were needed to make the Khans retreat.
The 3 families are just petty raiders that have been converted by House. Two of the 3 families have already shown disloyalty to House anyway.