I am sure the sound of two loud bangs from directly beneath a carriage accompanied by smoke would be more than enough encouragement for me to voluntarily vacate the train with all due haste. As for passengers being terrified or forced to flee rather sounds a bit like someone engaging in some journo alarmist hype.
It will be quite interesting to see what the DLR staff find went wrong.
I feel sorry for the poor passenger service agent in this situation - alone, initially, responsible for a train full of hysterical passengers, a smoking train and an unstaffed platform. The situation could have been a bit more troublesome had it occurred in a tunnel.
All the DLR tunnels have emergency walkways so evacuation is still possible if necessary, and as there is a below-ground station at at least one end of every tunnel on the system there would be additional staff not too far away if required. Still wouldn't have been somewhere I'd want to experience it mind you.
The essential things in life are seen not with the eyes, but with the heart. --Antoine de St. Exupery