you know someone can risk to die in a single stun with a dk and warrior with cds up on him, i remind you teleport doesnt work while being stunned nor silenced. the dk could have easily applied strangulate to the warlock so he could do nothing, death coil or teleport, even if trinketed..
and even if he managed to teleport in time, what would happen then, the warlock is 30 yards away with 20% hp and not able to heal anyway, just delayed his death by 2-3 seconds?