Although I'm a pilot, I am a very big proponent of professional flight engineers. Generally they are not pilots, but were flight engineers from the start - many from the military. Most have A&P licenses and have been doing the job for many years and know their aircraft inside out. In emergencies they help by taking care of the airplane problems which allows the pilot to concentrate on decision-making and aircraft control.
PFE's - worth their weight in gold in my book. Too bad it's a dying profession. I'll bet if the Air Transat had a PFE on board, they would have had a uneventful SE landing in Lajes instead of a white-knuckled shocker.