Well, one can argue about whether it was the best idea, but I don't think it was pointless: by the time you get to level 30 in FO3 you're God of the Wastes; some sort of challenge was needed because of the extended level cap.
Having massive hit points didn't make them a challenge just annoying. They could have halved their hit points, made them immune to knock down and poison and just further upped their attacks even further. Maybe give them a knock down effect. That would have made reavers a challenge. Instead of a bullet sponge eliminate the cheap shots [knock down and leg crippling from the dart gun] and give them a cheap shot attack.
