It's beginning to sound like that the structural design of the A300B4-600R could be at fault.
Remember, these planes were built in time when structural parts being bonded together with adhesives were still a relatively new idea. There has been quite a lot of concerns from mechanics about the quality of the adhesive joins in the long run. It's small wonder why Boeing has not really used adhesive joins until the 777 program, more or less.
I think there's a possibility that structural failure of the vertical tail--which ripped it off the plane--caused the plane to undergo severe aerodynamic yawing and structural stress, which eventually broke up the plane.
It appears that Airbus may have to issue an immediate directive to all A300/A310 operators start inspecting all structural joins very closely.