This isn't putting healing as a secondary perspective...
It's knowing the potency of our healing skill, mana management, knowing the approximate damages a tank is taking.

When you know what the damages mobs can do to the tank, you know what skill you have to use.
This isn't making dps or healing a priority. It is knowing to do both at the same time to be as much effective as possible as party member. That's the difference.

But it's really seems to be a useless debate.
You're not healing in the game it would seems, but still want to make me believe that you know better what we should do.
Then stick to your opinion then...

I have gently tried to explain you why and how but even if I main healer, i'm still wrong.

So well, good then.
Then I'm out of this debate.