Isn't typhon only like 25% attack buff at max compared to Jorm's 40% attack?
EDIT: Also, I generally agree with you - but that's the caveat against easier opponents. Against harder opponents, more hp can increase your damage by allowing your starter Eidolons to survive damage that would otherwise be fatal. So I think assuming all else is equal, extra burst damage is better for easier raids where your Eidolon is not threatened and extra hp is better for harder ones where your Eidolons may die.