I do not believe that it is always as simple as that.
If we take the example flown by FE HOPPY
This of course neglects the TSFC which could have an effect of the speed if your engines are running in a poor speed band.
With all engines operating the thrust required at Vmd may be too low to enable the engines to run an an efficiently high RPM. In some types of patrol aircraft the best endurance is achieved by shutting down some of the engines to enable the others to be run at a more efficient RPM.
But if we were obliged to continue to use all of the engines the best compromise would be at a speed greater than Vmd to enable the engines to run at a reasonably efficient RPM, without incurring too much extra drag.
In this case the problem is one of having too much installed thrust at Vmd. But the way that thrust and TSFC vary with airspeed depends on engine type (turbojet, low by-pass turbofan or high by-pass turbofan).
So best edurance could be higher, lower, or at Vmd.