Can we stop punishing shield healers for playing together?

[Rilifane]

Why is it "obvious" that GCD shields don't stack, when GCD HoTs from WHM and AST do? I guess SE doesn't want to add that cushion to barely-survivable tankbusters, but then the question is does the content need to be designed that way?

"Effect cannot be stacked with Eukrasian Prognosis or scholar's Galvanize."
"Effect cannot be stacked with certain sage barrier effects."
SGE and SCH tooltips. So unless the tooltip specifically mentions it, shields from SGE and SCH stack.

Edit: Also, what of the issue of gaining addersting stacks for Toxicon, especially if there's two sages in the party?

Shielding solely to gain Addersting stacks is a dps loss and usually ends up being a wasted GCD. If a shield is absolutely necessary anyway because there is no other way to keep a person alive, than Addersting is a nice-to-have slight damage return but that's it.
I'd like to see situations where you have two SGEs in a party but both need to GCD shield single target.

Edit 2: I don't know what kind of groups you play normal content in, but I do it through DF. Every so often I land in a group which just can't do mechanics, eats damage like a sponge and dies all the time. In those situations I'd really rather my tools didn't conflict with the other healers'.

I DF pretty much everything. I've done Trial roulette every day since early access and -surprise- landed in the EW trials everytime with most if not everyone except me being first timers. So I get the same chaos everyone gets in DF and dbl SGE or SCH/ SGE was perfectly fine. There was no issue at all.
You see your co heal always shielding? Don't shield, easy as that. You have enough other tools in addition to Prognosis on SGE and ET on SCH.

Edit 3: I could do a whole rant about how healer design in this game is bad and why does SE give us so many GCD heal buttons which end up sitting unused most of the time. But this shield thing happens to be what irks me right now.

Every healer only has exactly 4 GCD heal buttons: weak ST heal, strong ST heal, weak aoe heal, strong aoe heal; except with SCH with only "strong" aoe heal.
WHM Lilies are an odd case as they are more comparable to how other healers' oGCDs function. We have an overabundance of insanely strong oGCDs but GCD heals are comprably few, weak, and generally to be avoided if other tools are available.

GCD shields not stacking is by far the least of my problem with current healer design.
Healers have a lot of problems but that's definitely not a pressing concern.