Haven’t the Russians countered laser defenses by making their missiles with a highly reflective / heat-shielding outer coat?
I do not believe it.
They may have, although I don't think so. But in any event it would not help. Might make the damage worse. That's not your laser pointer. The beam carries lots of momentum, It kills not so much by absorption of the energy in the beam, but rather by momentum transfer, just like a really hot bullet.