Thank you for allowing Solid Fog -5 Reflex Save to work on raid bosses, it will be a great help to Evocation casters on the more difficult raids.
However the -2 to attack and damage roll, as well as the concealment, should also effect raid bosses. I've never really understood why the concealment effect from some clouds worked on raid bosses and others did not, and I think it is time to level the playing field a bit.