Just wanted to bump this - I noticed the same thing tonight. Had a drone get knocked down to 3 engines, but it still managed to keep with my lead at full throttle.
...that was just before the server crashed and I lost over 300 B-29 perkies.
Just FYI, a server crash will not cause you to lose perk points. Perk points are deducted from your account when the sortie ends. If you lost connection, then you would lose your perk points, but that is not a server crash.
The only time perk points are deducted is when the sortie ends normally, or if the server detects your computer is no longer available on the connection.
As to the reported issue. I am pretty certain the drones are designed to keep up with the pilot and only reflect the damage they take when the pilot takes over the drone. If that is not the case, then we could have a bug.