Fifth Element said:
I agree it should be presented that way if it were a substitute for a melee attack. But for the last time, under this interpretation, it's not a substitute for a melee attack, it is a melee attack.
But if Sunder just means using a melee attack (no matter what source that melee attack derives from) to attack a weapon or shield, then if you wanted to Sunder when you had a standard action available, you'd take the Attack (melee) action, and declare the weapon or shield your target. There wouldn't be a Sunder entry on the table of standard actions, because you wouldn't need a specific standard action when the generic one would already cover it.
If we have a standard action that means 'make an attack just like the attack action, except that you have to aim it at a weapon', then logically we'd need a full round Sundering Charge action - 'move up to twice your speed and make an attack just like the charge action, except that you have to aim it at a weapon'.
If you're saying that Sunder is just a melee attack aimed at a weapon or shield, which can occur in a standard action attack, a charge, a full attack, or an AoO, then its action type is variable... and it would appear as such in the table. Even though it's 'a melee attack' and not 'in place of a melee attack', it's still a variable type - giving it a separate standard action entry alongside the Attack (melee) standard action either makes no sense, or means a few other duplicate action entries are missing.
If it can occur as part of several different action types, it's Type Varies. If it appears in one place as a single action type, it isn't Type Varies and thus can't occur as part of several different action types.
In the Rules Compendium, it will apparently be Type Varies (and carry footnote 28), which means it can occur as part of several different action types. In the PHB, it isn't and can't.
-Hyp.