Attempting to disarm/start grapple etc isn't really the same thing imo, although I can see why you picked it as an example. A regular AoO doesn't provoke unless you choose to substitute the normal melee attack with a special attack that provokes. The SRD says. You normally provoke if u attempt to disarm, but the feat imp disarm negates the AoO.
I think the same concept applies to the attack granted by ray spells...Normally a ranged attack would provoke. But in the case of ray spells, you are substituting a 'ranged attack' for something that counts as no action, which resolves as a ranged touch.
Look at the spell Produce flame. It's specifically worded to work as either a melee touch attack or as a thrown weapon attack, which is resolved like a ranged touch attack. To my knowledge it is the only such spell worded this way. To me this means you can threaten out to your natural reach and make AoOs with it, but if you make a ranged attack with it its as if you were throwing a weapon which DOES provoke an AoO. That attack is just particularly accurate, hence the touch AC.
The SRD says:
Touch Attacks
Touching an opponent with a touch spell is considered to be an armed attack and therefore does not provoke
attacks of opportunity. However, the act of casting a spell does provoke an attack of opportunity.
Touch attacks come in two types: melee touch attacks and ranged touch attacks. You can score
critical hits with either type of attack. Your opponent’s AC against a touch attack does not include any
armor bonus,
shield bonus, or
natural armor bonus. His
size modifier, Dexterity modifier, and
deflection bonus (if any) all apply normally.
It seems pretty clear that ranged touch spells count as 'Touching an opponent'. The only distinction I see between the 2 is that you cannot make AoOs with ranged touch spells, because AoOs are explicitly only melee attacks. If this text is a contradiction to the table calling for the AoO, then doesn't the text automatically trump the table?