I've been using a two developer regime for a couple months now with MG-IV Warmtone Fibre.
Dev 1: D-73 (2:1). A hard developer to get the 'bite' in the shadows. Usually about 20 - 30 seconds.
Water Bath - sometimes, of about 1 min to let the D-73 max out. Other times just right into Dev 2.
Dev 2: Selectrol Soft - home brew. A ratio of 9:1 for anywhere from 5 minutes to 30 minutes.
I find the hard developer in first position sets a deep black and will carry up into the greys as long as I want it to. The 2nd dev will bring the highlights down to meet the Black where I want it to.
The system is entirely judgemental, proving once again there is no one way to make a print.