That's got nothing to do with not being caught by Genjutsu.
OT: Madara still wins. Normal fire has approximately 2000 degrees of heat. Katon: Gouko Mekkyakku was the size of Juubi. Juubi's size is 61.2 meters. 2000 x 61.2 = 122 400 degrees is the heat of Gouko Mekkyakku. Quite hot to the point where Raikage's body is not withstanding that much heat.
I'm tempted to neg rep you.
First off - you're trying to use real world physics for a fictional universe, and you try to apply an absolute size to the juubi when one can only gauge it's length relative to other objects since Kishi never stated the juubi's size. Second, your calculations make no sense. You don't multiply the temperature of "normal fire" (whatever that means) by the size of the fireball to calculate its total heat. Lastly, you decide on your own that "the Raikage's body is not withstanding that much heat." That's your own judgement and feats contradict that statement.
If you want to use "real world logic" then here's this: the Third Raikage's body is covered in lightning armour. Lightning is
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The sun is much bigger than Madara's fireball. Therefore, Raikage can tank the sun's heat so he can tank a fodder juubi-sized fireball from Madara.
(also, the sun's surface temperature is about 10,000 degrees Fahrenheit, so unless you're claiming that Madara's fireball is ten times hotter than the sun, your calculations are bullshit.)
Edit: never mind, didn't realize you were trolling.