I'm not certain on this, but my impression was opposite of yours.
Unearthly Glare states, "No Assault is resolved at the wall section..." Since, resolution of orders happens during the Assault phase, my thought was that the order is never resolved. Thus, the goblins do not die, and the order is returned to the supply at the end of the turn, without effect.
I think you're right.
Sorry for my precipitated answer. My bad.