You could have sticking calipers or slider pins as mentioned, but i would think you would feel it. Especially in the yota. It's a light handling rig that tires makes a big change in the feel. Dragging brakes or loss of rear brakes is something I think you would say something feels abnormal. Go for a high speed drive then slow with only the transmission, using the parking brake to stop, then temperature gun the rotors to see if any heat is there. That will show any drag.
Back with the gmt400 fleet we found the longest lasting rotors were the factory. Putting over 100,000 miles a year on many of the trucks guaranteed many were drivin hard. We tried every brand rotor that was available back then. Including slotted, drilled, both. The best results we had was having the factory rotors drilled, well, water jetted anyways. But it didn't help enough to be worth doing. We just had to accept that being under rougher than average conditions meant a set of rotors (pads also) didnt last as many miles for the application.
Toyota is on point with quailty parts. It wouldn't surprise me if no brand does better than the factory for it. I wont question her driving skills she is a smart gal, nice too. But in over 200,000 miles on the suburban we had back when we met at your place, that mountain is the only time I ever heated up the transmission. It is easy to see wearing the brakes a bit faster than average. Especially when half the country is flat and people drive slow compared to what we are used to.
As for the drilled/slotted ones you have now, contact the supplier or mfr. about replacement. Maybe a partial reimbursement if they won't pony it all.
Remember anytime you install new rotors, pads, or both to burnish them. It makes a difference. And I onow not applicable to you, but for others learning from this in the future: drilled and slotted rotors are a huge no-no for muddy or sandy applications. The air holes and pockets just turn into sand paper and wear out pads in no time, often scoring the rotors. I have seen a person try mud bogging for the first time ruin it all in half an hour.
Anyways, pull the rotors off and show some pics. Mic them or at least strait edge with sunshine behind (no not the eclipse on monday). Could be the trapped heat scenario. When after some descent heat build up you come to a stoplight and sit there with foot on the pedal. It lets the rest of the rotor cool quicker than where the brake pad is in contact. Freeway exits are bad for this, your mountain cant be any better. This could be why the faster cooling drilled rotors warp quicker than normal ones.
