As a dps I do agree we need to tone it down to match the tanks threat. As a mage if I see on the first pull that my blizzard is sending out an invitation for a slaughter I start single target dps.
General rule of thumb
Tank dies ->Healer's fault
Healer dies - Tanks fault
Dps Dies -> their own damme fault.
Try giving advice but at the end of it you want to get those 2 badged asap. Roll with the situation since its almost 15-20 mins wait time as a dps.