Only a bad played destro lock will use up your one ember on a full health target like that after that you have lost a powerful heal, your execute and other abilities if you every knew how to play a lock you dont empty your resources off the bat unless you know its a kill and yes still ramp up time considering you need to set up the burst still if you pop everything and it gets reflected,pally bubble, iceblocked anything like that your pretty screwed and wont have the chance to cast it again vs good players.