Damage scales from the center of the explosion to the outer radius with an inversely square progression. This means that it drops very quickly. The initial tuning I did for explosives was based off a misunderstanding of how the explosion radii worked. I addressed the Missile Launcher and Fat Man for the most recent patch, but did not get a chance to tune other explosives.
EDIT: Also, the Gobi doesn't hit an area the size of a small city park. Fat Men and Missile Launchers aren't intended to be used against single targets. From the way some of you guys talk, I get the impression you won't be happy unless Fat Men/Missile Launchers one-shot every BoS Paladin in T-51b and Deathclaw Alpha Male in a 100 yard radius.
Firstly thank you for replying and clarifying

Secondly also thanks for tuning the Missile Launcher and Fat Man.
Thirdly are you planning to tune the other explosives at a later date then?