The only way the design for healers will ever change from what it is is if they change the way damage is dished out during encounters. Yes ogcd's are way too potent, but the reason they are is due to how scripted all the damage is where you can literally plan out all your healing just from your oGCD's alone. Unless they start baking in pulsing or consistent aoe damage throughout a entire encounter healers will continue to stay the way they are. As much as I'd like to see healers change to the point where they can efficiently spend most of their time actually healing, re-designing how damage is presented in pretty much all group content to get healers to spend more of their time actually healing probably isn't going to happen anytime soon sadly.