Good healers put out every last bit of USEFUL healing they can muster, IMO.

Take Alysrazor as an example. Assuming it's not a one-shot, as a Disc Priest, I can inflate my numbers enormously on that fight by building up a 50+k Divine Aegis on everyone before the pull. Constant PoH spam before the pull is boring, but I can do it.

If I don't do that, my Resto Druid buddy can pop Tranq during the big initial AoE to inflate HIS numbers. (Obviously he can Tranq even if I do build up shields, but the numbers won't look nearly as pretty.) Tranq won't be needed again until the Burnout phase, and the cooldown will be up by then, so there's no reason for him not to use it.

He cares about the meters, I don't, so he Tranqs and I twiddle my thumbs. Everyone's healed up to full regardless, and we're both still at full mana when the real damage goes out. The job's been done without over-extension of resources; does it really matter how we got there?

I could, however, make myself look better and make him look worse if I wanted. I think /that's/ what's called snipe healing, when the heals would have gone out in any case on non-threatening damage, and there's absolutely nothing extra to be gained except gratification of the ego.

Always pushing yourself on the meters can be a good thing to a certain extent. Beyond that, it's silly -- for instance, my Resto Druid buddy apparently had a /cancelaura macro for my shields back in T11. I'm sure it did up his numbers slightly when he used it, but did it in any way make him a better healer than when he refrained from using it?

To me, snipe healing is cross-healing that goes past that extent. I don't think it's particularly productive, but YMMV.