Why do you insist on bring L/D none dimensional ratio into it and TAS its not required and adds nothing to the relationship of rate of decent to weight.
TAS comes into picture because both the aircrafts are flying at a common limiting descent speed.
And rate of descent comes out to be
ROD = TAS / (D/L)
How can one ignore this important non dimensional characteristics?
@keith
I have made the edit in the original post. Thanks for pinting out.