With the new data gather by sp00n, it appears that my original assumption that

=0.956 is constant is not true.
So far we only know that for a 70 rogue,

=0.988, and for a 60 warrior,

=0.956
Does k change with class or level? I think I need to go back and take a closer look, more test data from different classes and levels would be helpful.
Edit: Checked again with data from 80 warrior, and confirmed that

=0.956 for warriors.
It seems that k is also dependent on class but not level.
Edit2:
A quick recap on what we know about the DR formula:

is the diminished stat before converting to IEEE754.

is the stat before diminishing returns.

is the cap of the stat, and changes with class.

is is a value that changes with class.
Warrior and Paladin:

=0.956
Druid:

=0.972
Death Knight:

=0.99356050
Rogue:

=0.988
