if batman and robin are adjacent to a single character and are eligible to use vault can they use the first duo attack and then vault to a different sqaure and make the second duo attack against a different character they werent orginally adjacent to?

No. Vault can only be used at the resolution of an action - in this case, the power action given to activate the Duo attack. You can only Vault after both attacks have been made.

Actually Vault won't even work then. Duo attack is a Power action that only grants 2 attacks. Vault only works with a close combat action.

DUO ATTACK (optional):Give the character a power action to make a duo attack. It makes two separate attacks against opposing characters as free actions (making two separate attack rolls). These attacks may be close combat attacks, or ranged combat attacks with a single target. Resolve the first attack before making the second; the character’s damage value is modified by –1 for the second attack, to a minimum damage value of 1. If the character is kOd as a result of the first attack in a duo attack, thesecond attack is not made.

Vault 3 Points
Sets:Sinister
Prerequisite: Combat Reflexes or Leap/Climb
Choose a character. After a character resolves a close combat action, it may be placed in any square in which it may legally be placed adjacent to a target of the action at the same elevation as the target.

Tarnish

Good catch... I was going on auto-pilot.

Also, is it not true that you can only target a SINGLE figure with Duo Attack?

No. The line you are thinking of means that you can only attack a single target with any given portion of the Duo attack (so Batman and Robin can't use their dual targets), but nothing in the Duo rules states that you can't switch targets (or even ranged vs close combat) between the two attacks granted by the Duo ability.

Thank you.