To be fair, that's strictly your opinion. I don't share the same belief as you. You think RD is based on a "guess, arrogance, and wishful thinking," which simply isn't true. No offense, but most of the posts I've seen on here about RD are pretty ignorant. I would respect opinion's about RD from people if they took a class and dove it for awhile than those who simply read a thing or two about it.
I completed several hundred dives, including shallow training dives, in my UTD years. I was certified at Tech II. I took my Ratio Deco class from Andrew Georgitsis. That was a long time ago. I am honestly trying to understand what the current thinking is here, and this is your chance to show everyone what that is.
Below you will find two dive profiles from Multi-deco ZHL-16 C with GFs of 50/80, which is what I am currently using. The first is for a simple freshwater dive using 21/35 at sea level, and the second is the exact same dive at 6,000 feet. (I did it with 2 deco gases; I can change it to 1 deco gas if you prefer.) When I was with UTD, we would have done them both the same, but you say things are different now, and UTD will change practices at altitude.
Could you please post what those two dives would look like in current UTD practice? It doesn't have to be you who answer--any of the other UTD instructors reading this thread can fill in the information.
Elevation = 0ft
Conservatism = GF 50/80
Dec to 180ft (3) Triox 21/35 60ft/min descent.
Level 180ft 27:00 (30) Triox 21/35 1.32 ppO2, 85ft ead, 105ft end
Asc to 80ft (33) Triox 21/35 -30ft/min ascent.
Stop at 80ft 0:40 (34) Triox 21/35 0.71 ppO2, 30ft ead, 40ft end
Stop at 70ft 1:00 (35) Nitrox 50 1.53 ppO2, 32ft ead
Stop at 60ft 2:00 (37) Nitrox 50 1.38 ppO2, 26ft ead
Stop at 50ft 3:00 (40) Nitrox 50 1.24 ppO2, 19ft ead
Stop at 40ft 4:00 (44) Nitrox 50 1.09 ppO2, 13ft ead
Stop at 30ft 6:00 (50) Nitrox 50 0.94 ppO2, 7ft ead
Stop at 20ft 8:00 (58) Oxygen 1.59 ppO2, 0ft ead
Stop at 10ft 14:00 (72) Oxygen 1.29 ppO2, 0ft ead
Surface (72) Oxygen -20ft/min ascent.
Elevation = 6,000ft (s)
Conservatism = GF 50/80
Dec to 180ft (3) Triox 21/35 60ft/min descent.
Level 180ft 26:53 (30) Triox 21/35 1.32 ppO2, 85ft ead, 105ft end
Asc to 80ft (33) Triox 21/35 -30ft/min ascent.
Stop at 80ft 0:40 (34) Triox 21/35 0.71 ppO2, 30ft ead, 40ft end
Stop at 70ft 1:00 (35) Nitrox 50 1.53 ppO2, 32ft ead
Stop at 60ft 2:00 (37) Nitrox 50 1.38 ppO2, 26ft ead
Stop at 50ft 2:00 (39) Nitrox 50 1.24 ppO2, 19ft ead
Stop at 40ft 3:00 (42) Nitrox 50 1.09 ppO2, 13ft ead
Stop at 30ft 6:00 (48) Nitrox 50 0.94 ppO2, 7ft ead
Stop at 20ft 7:00 (55) Oxygen 1.59 ppO2, 0ft ead
Stop at 10ft 25:00 (80) Oxygen 1.29 ppO2, 0ft ead
Surface (80) Oxygen -20ft/min ascent.