The ADG4 is a very simple but effective way to spread the light over a very wide area. While it does diffuse away 2.5 f-stops from the hottest part of the non-diffused direct reflector, it also spreads the light coverage from about 60 degrees to over 180 degrees.
It is not perfectly even on a reflector in order to allow you to still aim the light where you want it the strongest, but it is perfectly even if you mount it "bare bulb" for that purpose.