There is a month old report that appears to hint at a specific failure that we have not been discussing:
Preliminary Findings Point to Flap Problem in Tu-154 Crash | Defense News: Aviation International News
There is a background statement that may be relevant:
An SPZ-1A sensor device is used to monitor whether the flaps move symmetrically; if they do not, it de-activates the hydraulic actuator and issues a warning to the crew to assume manual control. The Tu-154B-2 flight manual and other documents prescribe using an electrically-controlled stabilizer and control yoke to offset the diving force that the flaps generate should they have not retracted. Crews are required to perform simulator training to deal with such a situation. If the failure of the flaps retraction mechanism is discovered in a timely manner, the pilots are instructed to land at the nearest airfield while maintaining a relatively low speed. They are also instructed to keep the throttles at a low setting so that the engine thrust does not further complicate the issue of aircraft stability and controllability.
So what would be the result of overspeeding extended but deactivated trailing edge flaps? Could that be a reason the aircraft did not climb significantly?