A character's combat ability, reaction and brawn should all affect how they take damage.
They already do that. When you block, you roll Fighting to cancel damage; when you dodge, or try to cushion a fall, you roll Agility. If Fighting and Agility
also contribute to the calculation of Health, in a sense it's as if they were factored in twice, both actively and passively.
My question is, why should a superhero with Strength 2, Agility 2, and Fighting 8 (Astounding) not survive a Blast 12 explosion or a fall from a tall building?
Because I'd expect Fighting to help him
in a fight, not in every situation. You don't
fight gravity, or an explosion. Now if that character had Strength 2, Agility 8, and Fighting 2 instead, he would indeed be able to very likely survive damage from a Blast (by dodging it) or a fall (by rolling Agility), making the contribution of Agility to Health redundant.
Beyond the thematic reasons, I also find odd that the way Health is calculated now, Strength only contributes 1 point for every 2 ranks. I would expect a
much greater divide in Health between different levels of Strength. I mean, with equal Agility and Fighting (let's say 3 for both), I find it super weird that a weak-ish human (Strength 1) and a super-soldier who can lift up to 1 ton (Strength 4) only have a 1-point difference in Health (4 for the weak human, 5 for the super-soldier).
It is not our part to master all the tides of the world, but to do what is in us for the succour of those years wherein we are set, uprooting the evil in the fields that we know, so that those who live after may have clean earth to till.