This is expected healer behaviour.
If someone dies: Were they standing in a bad place that everyone else knows was bad, and perhaps repeatedly?
Yes = Their fault. (This is not specifically a DPS fault since Tanks and Healers can fail this too.)
No = Healer's fault.
Exception is if tank isn't using mitigation abilities when expected, or isn't holding aggro, in which case Tank's fault.
When is it specifically DPS's fault?
a) When you die to boss enrage.
b) When tanks AND healers run out of mana and/or cooldowns. (<--if this happens DPS might be eating crayons)