How can I hang a large mirror on an uneven (warped?) wall?
I'd simply install washers behind the clips to act as standoffs. Be sure your screws are long and stout enough. Use washers as needed to create a small gap behind the mirrors at all mounting points, allowing alignment between mirrors. 

This could create a visual bounce/jiggle effect if the mirrors aren't stiff enough. Use balls of poster putty or other flexible material at several places across the backs of the mirrors to act as anchor supports. This will also provide structural support in the event of an accidental collision.