This is how it has always been, that's why you didn't see SCH/N.AST pairs in previous expansions. I can see why they wouldn't want to change this, as they ideally want to keep one barrier and one pure healer per party.

That being said, SGE/SCH is still very viable and content so far, perhaps with the exception of P3S/P4S, doesn't actually require GCD shielding. So you should never really be in that predicament. It probably is very annoying though, but it is what it is.