Amen.
The other day, warlock joined a pug for a leveling dungeon. Didn't soulstone anyone, didn't hand out healthstones. Before a pull, they didn't replenish mana by drinking, but life-tapped down to 20%, then used Rain of Fire immediatelly after the pull, pulled aggro, but got saved by a timely BoP. They got advised by the tank not to do that again. Next pull, they of course life-tapped down to 20% again, used Rain fof Fire, pulled aggro of several mobs. Died, the started to whine about healer sleeping on the job.
Vanilla is not WotLK, with opulent tank AoE threat generation, 40k mana and holy Lights hasted down to 1.5 sec critting for the whole health bar.
Allow me to add the supplemental rule #1 to the Mantra: You can't heal stupid.