We report radiotracer diffusivities in a Pd43Cu27Ni10P20 melt, presenting for the first time a complete set of data for all components over the whole relevant temperature range. While a vast decoupling of more than 4 orders of magnitude is observed between the diffusivity of Pd and of the smaller components, at the glass transition temperature Tg, the diffusivities of all components merge close to the critical temperature Tc of mode coupling theory. For Pd, the Stokes-Einstein relation holds in the whole range investigated encompassing more than 14 orders of magnitude suggesting the formation of a slow subsystem as a key to glass formation in systems with dynamic asymmetry.