Tested in the most recent Krastorio and Factorio-Version.

The changes for the atomic bomb wave in the "damage-and-ammo".lua have the term "damage=" two times, and thus do only the radioactive damage.
This lowers the damage of atomic, heavy and antimatter-rockets significantly.

Line 517: data.raw["projectile"]["atomic-bomb-wave"].action =
{
{
type = "area",
radius = 3,
ignore_collision_condition = true,
action_delivery =
{
type = "instant",
target_effects =
{
type = "damage",
vaporize = false,
lower_distance_threshold = 0,
upper_distance_threshold = 35,
lower_damage_modifier = 1,
upper_damage_modifier = 0.1,
damage = {amount = 400, type = "explosion"},
damage = {amount = 100, type = "radioactive"} <--
}
}
}
}

I will test it better when we decide to release the next update but, because the bomb create many clouds that each made damage, I think that it's ok for now. And, is right that the antimatter/next tier, do more damage.

Thanks, it really was broken. Will be fixed in the next update.

I'm currently on the latest version, has this fix already been out yet? As the problem is still there

Still not, in the later version, we have change the definition, they don't overlap are different actions that act simulatney.

Ah okay, thanks for the update!