Auto throttle

[Lackomar]

On autopilot descent, aircraft is over speeding (Xbox)

[7heAngryVe7eran]

If your descent rate is too high, even with the engines at idle, the aircraft will overspeed. Please check and adjust your descent rate and/or use spoilers to slow down.

Also, the autopilot may be attempting to descend fast enough to meet certain altitude constraints. In that case, the upcoming avionics update may address some of these issues.

[Lackomar]

Shouldn’t descent be regulated by the FD.?

[RicardoLVFR]

Shouldn’t descent be regulated by the FD.?

What mode are you using for descent? Open descent or DES (VNAV)

if you use open descent it will slow down and descend on the selected speed, if you do DES mode it may overspeed as the A330 is kind of a glider and if you don't do any speedbrake it may happen.