The main advantage of the E.I-III series is that it was a gun platform which the entente had no answer for at the time. It was not the fastest, most maneuverable or reliable plane for its time, it was just capable of bringing a lot of firepower to a target in close range and wreak havoc.
Other than that aspect, it was a death trap for the inexperienced. Keeping in mind... aviation was only 10 years old when the E.I was first taking flight.
The wing warping concept was the flavor of the day, which is probably the WORST way to control an airfoil. Given that, one would expect the E.I/II/III to be very difficult to fly.
I think the E series FM in WOFFUE is spot on for what you would imagine out of a such a primitive plane design.
All the best,