I'm sure that I'm not the only one who's noticed this... it's something very strange that's quite noticeable in the later FFs, particularly FFVII and VIII. It has to do with the assigning of elemental attributes to a character's weapon and defences.
Let's look at a situation where one character - Squall, for instance - has an 'Elemental Attack - Fire' rating of 100%. Rinoa has an 'Elemental Defence - Fire' rating of 100%. She's totally immune to Fire magic, she'll actually absorb it.
Let's then suppose that Squall attacks her with his fire-elemental Gunblade. She'll gain HP, absorbing the damage. To me, this is just absurd. No matter how flame-proof you are, it's still going to hurt if someone shoots you in the face, or hacks at your body with a whopping great sword. The same applies for any element - just because a character is immune to the Poison element doesn't mean that they should be invulnerable to any bullets, clubs or pointy sticks that happen to be carrying poison.
Am I the only one to whom this situation is just a little strange? A minor gameplay detail, but one I felt like mentioning for no real reason.