The other extreme

[Rawrz]

Why top someone off when everyone has a natural regen. Heal on a non active battle time? of course! When active though, if the dps arent going to be in danger, theres no need to heal them. Understanding rate of damage is half of a healers role. Might as well sit my controller down and tie my shoes in a dungeon. Equally as relevant as topping off someone who wasnt in danger of dying.

[Sylvain]

Why top someone off when everyone has a natural regen. Heal on a non active battle time? of course! When active though, if the dps arent going to be in danger, theres no need to heal them. Understanding rate of damage is half of a healers role. Might as well sit my controller down and tie my shoes in a dungeon. Equally as relevant as topping off someone who wasnt in danger of dying.

While this is not a practice I actively do, I think you're right.

But I would be cautious with such practice, as you pointed, if you know absolutely Nothing is going to happen, in fact, why waste your time healing when you could help finish the boss.
On the other hand, if someone die because of that, even if is technically their fault for failing a mechanic, the little dps you will have pulled over the 2.5sec it would have taken to top the dps is not worth it.
I think of the "do not move" mechanic from the spider boss in Baelsar Wall or the big cleave from Griffin. If one dps dies because I choose to do 1-2 more MaleficII instead of topping them right away, while it's technically their fault, I'm also to blame as my choice will result in his death and less overall group dps.

Of course, this is considering pug situation with people you don't know.
At the contrario, when my friend tanks he informs me if he's gonna pop invincibility or if he'll ever need any heal. Knowing that, I'll spam gravity to get faster.
I'll be much more conservative and careful with a pug tank that doesn't talk.

But fundamentaly, Rawrz is right. If there's better window to heal people and they're safe even at low health, you might as well use those Windows (for instance, Bismark shell, technically no one should die while we are all dpsing, everyone falls very low though, but there's no need for heal at this moment)