Their special power states you can place them next to the highest point opposing character and use duo attack as a free action. They also have exploit on this click. Does duo and exploit work?

You cannot use Exploit Weakness with Duo Attack. Exploit Weakness requires a close combat action be given to the character to use it. Duo Attack lets you make 2 close combat attacks as free actions, a close combat action is never involved in Duo Attack.

Ty for the clarification