Lord Pendragon said:
Right. Also, the AoO mechanic is an abstraction. The PC isn't just taking a single swipe when appropriate. The PC gains an additional chance of scoring a hit, because he's assumed to be constantly attacking the enemies within range.
I don't see that anywhere in the rules. And it is pretty easy to demonstrate the opposite. A fighter can be busy fighting 2 enemies, but if a third one charges past, he gets an AoO against him. There is no 'constantly attacking' going on there.
Fighter can be fighting 3 enemies, and one trips and falls down. Fight goes on for more rounds....(only 6 seconds each) fighter is ignoring the one on the ground as not much of a threat, but still aware of his surroundings. When the enemy tries to stand up, the fighter takes the AoO.
AoO does not necessarily come from 'constantly attacking', it comes from being 'constantly aware' of you surroundings.
A PC cleric has just cast heal, and intends to deliver it to the sorely injured fighter on his next action. In the meantime, the PC wizard, also near death, runs past the cleric.
Now, should the cleric be allowed to deliver the touch spell on his hand as an AoO to the wizard as he moves through the cleric's threatened area?
Sure, why not. What is the difference to the cleric? Now, since the wizard was not aware of it, I would make the cleric roll to hit. (wizard is 'unaware' of the attack, thus no dex bonus)
The cleric is aware of his surroundings, and notices when someone runs past him, if he is a good guy, he lets him go, if he is a bad guy, he tries to hit him, if he is the near death wizard, he tries to touch him.