- Did someone in the party die?
If not, then we healers did our job.
If some1 died but we still got the boss, then I check if he died 'cause he didn't move from 'bad stuff in the ground' or because a problem with our job: he wasn't near a healer, we went oom, we hated him and wanted him to die, etc. I normally try to fix the problem by either moving or being careful with overhealing. This is easy if you can coordinate with the other(s) healer.
- Did we wipe?
If yes, then, and only then, I actually check everysingle re-counter I have. Did I overheal much? did I went oom or it was simply that the DPS sucked for the fight and we hit enrage? Since every fight is different there is no single method to know for sure what is always the problem. Maybe in some fight you didn't overheal and didn't went oom, but the dmg was so heavy that u couldn't control the spikes, or maybe you moved wrong and got 2-hitted to the ground.
There have been fights in which I'm called on for topping overhealing (like...getting 3 times the second place or something xD). I then point out that nevertheless I never went OOM, that I still got a close second place on actual healing and that 20% of the overhealing comes from echo of light.
As a great wise man once said: If it isn't broken, don't fix it. If you are progressing and nobody is dying, then you are fine.