Why? If a poison, bleed or burn is tickling someone and my regular heals cover it, I'm not going to waste a GCD on Esuna. I actually do take it off my main bar sometimes depending on the content I'm doing. If all I do is Savage and Expert on healer, there's no need to waste the slot. Obviously if I'm running content that needs it I'll move it back, but those situations are so rare I'll maybe need it once or twice a month.
I can't say I mind that much if they make it see significant use or not. You simply use it on certain debuffs. It didn't really make E8S more exciting for example. I think there are much bigger issues they need to address with healers.