Problem is using a gcd on a heal outside downtime is a fairly uncommon. Healing like aggro is a group effort and that is the issue. If healing remains a group effort those at higher levels of play will have very few active skills to use, if they up the incoming damage to forcibly increase the amount of gcds one uses on healing then they run the risk alienating their playerbase. It will be a balancing act and I personally do not think SE is capable of such an act.