Modern rotors are already internally vented for heat dissipation, cutting holes, slots, or dimples in doesn't pull heat out of the steel, the increase in surface area is negigable, fractions of a percent. Heat sinks add material and surface area to radiate heat, and we are talking huge increases in surface area, sometimes as much as an order of magnitude. Take a look at a regulator/rectifier, about 80-90% of it is just heat sink and it doesn't get nearly as hot as brakes.
I also disagree with the gearing. In first gear low range with stock diffs, I can hang on the engine compression at about 2-4 mph on very steep slopes 30°-45°. My vehicle was built in 2006, and while not exactly new, it is certainly not vintage.
Dimples, holes, and slots create weak points in the rotor that will prematurely fail. Heat isn't as much of a problem as thermal shock. A hot brake being splashed with cold water is far more likely to crack than a blank vented rotor. Those weak points don't give you are real benefit in braking performance. There is a reason trackday cars are typically run with blank rotors today - to prevent rotor failure.
If your brakes are getting that hot, you need to shift down a gear. Even after long downhill sections brakes should be cool enough to touch. I remember coming down Pikes Peak back in the day, they had a brake check station half way down. If your brakes were hot they made you pull over until they cooled off. They checked by placing their hand near the rotor to feel for heat and then touching the rotor or drum if it was cool enough. If they could touch the brakes, you were allowed to continue.
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