dungeon helpers

[Saseal]

In really low level dungeons (Sastasha, Tamtara, Copperbell) I generally only heal the tank if they get to like 60% when we're against Mobs.

I understand what you're saying, being the truly low level dungeons, and I agree with you.

--- in regards to my example situation (and just to further explain the situation before anyone thinks I'm one of those healers that cure when 10% of a tank's HP is gone...) - the person could have just tossed a CSed heal and it could have been fine. I might have a little bit of a hard time with trust, but seeing a tank continuously below 50% - hell, 30% - with little reaction is alarming.
("they're gunna cure. /shrug ....wait, they're gunna cure, right? er, ....right? please? Forget the fhdsjk treas-okay, I don't trust you. *Physick*"). In your case, if they're freaking out over 80%, then that's silly and they're freaking for no reason

But yeah. That's the only time I have done so, with exception to the healer getting overrun with lost ADDs and I just helped to heal them in a moment gone awry.
I don't believe in "heal all the time every time!" (I've seen it. It's annoying.) but not a fan of cutting down to the line, just because it's an easy dungeon, either (which wasn't the OP's case, so I don't feel the DPS' taking over healing was necessary, for them).