The highest peak of the Tian Shan mountain range tops only at 24,500' and the route is neither critical nor "dangerous" for a B744, which upon reaching the sector between REVKI and KCA [highest MEA], will already have burned enough fuel to easily maintain FL315 [9,600m] on 3 engines.
I'm not familiar with B772 single engine performance, but the higher peaks of this mountain range [which is not part of the Himalayas] is fairly narrow. In case of an ETOPS engine failure, an immediate turn off the airway to lower terrain could be achieved within 10 minutes during gradual "driftdown" [opeartated at MCT on the remaining engine]. Keep in mind that airplanes originating at MNL, HKG, PVG or PEK will already have burned off several hours fuel before reaching these peaks, so the airplane would not be struggling at max gross weight with an inoperative engine. And if maintaining sufficient engine-out altitude were a problem, then fuel could be dumped immediately and the airplane could be diverted to a designated ETOPS en route alternate airport.