Don't talk about things you don't understand, please.
We don't "refuse to cast GCD heal to push damage". If a GCD has to be cast for whatever reason it is, it will be (to keep people alive you know ?)
We spend our ressources properly/depending on the situation, which allow us to push damage.
And what you're saying is "congratz for understanding the game and your class very well, now be bored".
I'm not gonna panic press helios like crazy if I have earthly star on and the whole party inside.
I'm not gonna panic press Benefic II on the tank if a scholar put an Excog on him (and I have essential dignity)
I'm not gonna panic press helios if I know there will be no direct damage/threat until a certain time and Celestial opposition regen will top us off for the next mechanic.
I'm not gonna waste mana on GCD heal that oGCD will cover safely.
And those are example among others.
Have you ever wondered why we meet those WHM player, almost always low on mana, complaining "aww, it's hard to heal no mana, can't heal anymore" - "eww my co-healer is dpsing and let me heal everything"
No sweetie, you just don't use your toolkit correctly and don't understand how to play your class
And last note : we used to have more dots. Maintaining a dot for every 24/30s is not what I call "complexity". If anything, it's even better to contribute to damage this way than spamming what used to be a filler. Because by the time it ticks, the damage are here and you're free to do whatever you want, and if nothing's required => filler.
Now please...