Mercer in no way, shape, or form, scales to the SH, though the reverse is true. Regardless, the nuke itself was on the high end of 7-C, where the difference between the low end and high end is 17.5x.
Regarding the thermobaric bomb, "Their reliance on atmospheric oxygen makes them unsuitable for use underwater, at high altitude, and in adverse weather. They are however, considerably more destructive when used against field fortifications such as foxholes, tunnels, bunkers, and caves—partly due to the sustained blast wave, and partly by consuming the available oxygen inside."
I'm also assuming you've read at least that portion of my blog, where I went with the destruction of the building instead of the multiple thermobaric explosions that went off, since you can't assume all explosions are the same without knowing the chemical compositions.
Heller is the size of a human and can rip a Goliath's head clean off. Your point?
According to your standards? It's impressive when you have millions of infected, which include Juggernauts, Brawlers, Flyers, etc, and vaporizing them on contact at that. That adds up.