You know what happens when a tank assumes healers know what they're doing? Wipes. Should always test the waters first to make sure your healer is up to the task, because a lot of them really will focus exclusively on DPS and let their tank drop down low enough that an auto could take them out. Conversely, you also encounter a lot of healers that won't DPS at all; they just spam healing spells, even when you're full.
