AC: is it worthless?

[JadePhoenix]

To my knowledge these ways include True Seeing (or Illusion Purge, but who casts that?) and Pierce Magical Concealment. Please enlighten me if there are more ways.

Blindsight and Mindsight both spring to mind.

In the case of True Seeing, you're either facing a demon or a caster. I agree that miss chances are useless in a demon-heavy game, but I'd call that a corner case. And if you're facing a caster with 6th level spells, True Seeing is just one of many, many things you have to worry about.

I'm not saying miss chances are useless, I'm just saying it might be countered. Also, there are items with true seeing, such as the Scout Headband, usually considered a must have items for melee characters.

In the case of Pierce Magical Concealment, I'd have to say the mage slayer line is also somewhat niche. If it isn't, then there's also Pierce Magical Protection, making both AC and miss chances null and void for the gish. At that point you just have to kill him first.

But that is exactly my point. You can counter both so you shouldn't depend on just one.