In the original system, 20% of your CP/RP are applied to your rank each week… so with 750K honor (65K RP/CP) you would earn 13K after a single week. This puts you at rank 4.
In SoM, 40% of your CP/RP are applied to your rank each week… so with 750K honor, you would earn 26K after a single week. This puts you at rank 7.
Under the new system, with an 8-week timeline, it will be closer to (maybe not exactly, but close enough to get my point) 33% of your CP/RP applied to your rank each week… so with 750K honor, you would earn about 21,450 CP after a single week. This puts you at rank 6.
You could reverse engineer the exact decay percentage in the new system using the information available to us, but that is going to take way more time than I have available to me at noon on a Wednesday. It might be 30% rather than 33%.