Or house rule it to go with your gut?
Our house rule was that anything that is blast or burst is a single attack that the rogue can choose to include his/her SA damage in. But, for things that would have multiple attack rolls the SA damage would only be applied once.
This carries into Hunter's Quarry and Warlock's Curse (because why then would you place multiple curses or quarries?). I know it might nor carry over very well to other groups, but if someone feels good about AoE sneak attacks go with it.
(Yeah, I know... warlock's pact triggers when a cursed enemy falls etc. But, I think it's good. Also consider, if the rules DID work this way, would it feel broken and be rejected immediately?)