i agree with Joxer's post. Besides anyway if I remember right one of the parts of this "INNER CIRCLE" mission is you have to destroy the red Lyrium crystals with Varric in your party anyway. Most of the INNER CIRCLE missions will require that specific character to be in your party to complete them and have them to be "glitch free" in case you wonder why a specific character or whatever isn't showing up.
BTW if I remember right there is a near identical mission to this where one you just have to find them while the other you have to destroy them. Maybe since the first one wasn't completed that is why there was a conflict?