I do not know the exact ratio of pure FLX plastic to ESP, but I believe I saw somewhere that of the whole FLX line, the Drone, or at least its earlier runs, were more ESP than FLX. We are talking something like a 75/25 mix. This would definitely make it more rigid while retaining the overall feel of FLX.
The 2008 Worlds was the hardest version while the 2009 LE were considerably softer. I never threw the 2010+ molds, so I cannot speak for them. I used the 2008 forever and it never showed any signs of abusive wear. However, I eventually switched over to the Z Drone because of the little extra glide and distance.
Since I have room in the bag I found that I completely pulled the Drone and replaced with a combo of Pig and Trident. A Pig powered up or the Trident powered down can accomplish fairly the same shots as the Drone and now I have the added bonus of what those two discs can accomplish otherwise. However, I will not trade away my Z Drones. If I ever need to blow up my bag and start over, the Drone is a great place to start for my mids.