Slaying Action + Sniper's Action

Question

Minor Action: Snap Shot
Standard Action: Standard Action Attack + Sneak Attack
Action Point - Minor Action: Ranged Basic Attack + Sneak Attack w/ Sniper's Action from Cloaked Sniper
Minor Action: Sudden Bolt + Sneak Attack w/ Slaying Action Feat

I ran across this combo the other day, and the more i look at it I'm unclear if its legal or not.

Sniper Action (11th level): When you spend an action point to make a ranged basic attack and you have combat advantage against the target of the attack, you can add your Sneak Attack damage even if you have already dealt Sneak Attack damage during this round. If the attack hits, you can shift 1 square.

Slaying Action
Heroic Tier
Prerequisite: Rogue, Sneak Attack class feature
Benefit: If you spend an action point to take an extra action and have already dealt Sneak Attack damage during this round, you can deal the extra damage a second time during this turn.

My issue is do these stack, do i get both instances of being able to use sneak attack granted by sniper's action and slaying action, or does one cancel out the other.
Also does the order in which the turn is structured affect which "action" the person would be able to use.

Answer 1

Slaying Action specifically mentions applying the extra damage "A Second Time" during this turn. While the order you have listed is questionable, I think if you were to spend the action point, then use the Slaying Action, then use the action granted by the action point to make another attack, there shouldn't be anything that stops this from using sneak attack three times (Sniper Action doesn't say second, it just says you add the damage).

The only thing I'd find mildly questionable is whether you can spend the action point but have it not used until later in your turn (if anyone knows this is explicitly called out somewhere as something you can't do please comment so I can adjust appropriately).

Of course, the person expended an action point and two encounters to make 4 attacks, three of which have sneak attack damage (and at least one of which has to be a RBA which limits it's power to just a little more than the sneak attack damage). It's good, but not gamebreakingly so given the ability to only do it about once every two encounters. I personally wouldn't have a problem with it even beyond the RAW concerns.

Edit:

One thing that would shut this down is if when Slaying Action says "If you spend an action point to take an extra action" it means use the extra action you got. That's not what I get from it, but if there is a more explicit use of the wording that means to use the action gained then that would leave you with the order you mentioned, which a strict reading of Slaying Action would shut down as it would be the third use of the extra damage, not the second.