Sorry, but I stand by my thinking on the altitude - thinner air is not very technical, but if you want to go that route, think of a potato chip bag or any other sealed vessel as you go up in altitude - as the air pressure all around the vessel decreases (atmospheric pressure) the air inside the vessel if it's sealed pushes on the walls of the vessel, in essence creating a higher differential. Not only have I never experienced any decrease in performance (recovery rate of the pressure) with the RVi in similar situations, but years ago had the CW unit marketed under Roadmaster, and it too used a pressurized vessel to push a piston out against the brake pedal, and it also performed fine under those conditions.
According to the owner of RVi, that unit is not designed to constantly be pressing on the brake pedal - and if you watch the tablet that indicates when it's pressing the pedal, it does not press constantly even under those type declines. What causes the piston to deploy is the accelerometer sensing a change in acceleration - deceleration in this case - and then it reacts accordingly. Once the vehicle slows, the acceleration must again change - decelerate - for it to sense it and deploy the piston.
Of course, maybe the difference we see is because I am doing this in a DP that has air brakes, so you don't pump the brakes like a lot of people do with gassers - hence I'm not causing that piston to constantly push the pedal so the demand for air is less. I actually found the piston deploying more in stop and go traffic once - but it still was able to keep up with the demand. I'll reserve comment on what you were told - there's other posters on this forum who have been told things by RVi customer svc that contradict what the posters found...
As for the Rubi weight - I have under 100 lbs in accessories added to the weight of 4439 lbs, and with my usual 1/2 to 3/4 tank of fuel I am still under 5K lbs. I don't carry much in the Jeep, so I don't worry about exceeding 5K - but you have a point in that you can quickly add a lot with gear, etc.
Your Diesel is the Game changer you can tow more weight and you have much better braking/speed control on inclines even without TOAD brakes. That is the issue with gassers even in tow mode 6% hill you will reach speeds of 60ish in low tow gear and engine above 5000rpm and then you need to brake to 35mph for the corners it takes a lot of pumping to stay under the 10 second rule to get that speed down with a gasser thus the pump on the RVI working over time to keep up. That is the challenge of these non progressive wireless systems when used in gas coaches that are towing at or over max GCVW. The other issue with the RVI and the Patriot is accelerometer it takes significant force before it really triggers especially if you are on a long down hill in lower gears then trying to gently slow down 30 mph for those corners. While the RVI and the Patriot does fine on the flats not so much under this condition I outlined which is why a wired progressive system is best. You simply cannot beat real progressive electric wired braking PERIOD on any rig wireless has limitations because of the wireless interphase... Again if i was flatland towing I likely would not be having this dialogue the wireless systems are good for that. Even the Blue OX Patrion 3 (their newest) I tried it for 3 weeks before returning it, it like the RVI is NOT progressive which is a challenge for long steep declines.