It's definitely half plate, your assumption is incorrect. Regardless, it was not missed. Paralysis and unconscious ignore the to-hit calculation, they auto-hit within 3m regardless of AC, even if immune to crits, to the best of my knowledge. The point in terms of magic missile and aoe effects is neither incorrect nor irrelevant. They are indeed not counted as to hit effects, and we are indeed talking about armor. Let's recap your assertions I was responding to:
"armor outperforms everything", "there is no enemy in the game that can hit you with an attack".
The point about there being non-attack roll based ways to damage you is that you are not at that point impervious to damage, and therefore, armor may not outperform everything. For example, Ketheric's Shield only gives +2 to AC instead of +3. But any Cleric or Sorc or other primary spellcaster who took the +1 Shield for +3 AC over the +1 to their Spell Save DC is missing out in a huge way and is *not* outperforming compared to other options. High AC is nice, but it's hardly the same as invulnerability, and there are absolutely effects more valuable than AC bonuses available on your gear.
