I wouldn't agree with everything you've said there flybubba, in both the Mach and the IAS phase, descent angle constantly increases.
(1) During the Mach phase, IAS is constantly increasing, with increasing drag, thus, both the Angle and Rate of descent constantly increase.
(2) During the IAS phase, drag is ALMOST constant, whilst TAS decreases. Thus the Rate of Descent is almost constant against a decreasing TAS, thus the descent angle constantly increases. Rate of Descent, whilst almost constant, will decrease slightly as drag reduces as EAS reduces for the same IAS with decreasing altitude. This latter factor slightly reduces the rate of increasing descent angle, but only slightly.
Regards,
Old Smokey