Not that this is going to help, but...
My experience with liquid rubbers of many different types makes me strongly suspect what Hot Toys is doing wrong: I think they are using a black pigment that is incompatible with the rubber type itself. The flex tubes and the domes are all black; I Don't think it's the glue, as some have supposed. The elbow and hip rubber has no glue involved, yet they are degrading just as the domes are. I think they are using the same recipe as they did in 2006, which includes a black pigment that reacts with the base rubber. When exposed to the air, oxidation causes the reaction to advance. (my theory)
WHY can't I work at Hot Toys, to research and produce accurate decals, AND to deal with the rubber intelligently???
Oh... because I'm not a money-grubbing bastard; I forgot.