I don't think the problem is altitude, I think it's habitat. When I first moved out west I hunted areas like you describe, with limited success. Looking back, the habitat in those areas was not as good as the habitat where I hunt now, and those areas held significantly fewer elk. For an area to hold large numbers of elk, IMO it needs a good mix of thick cover and open areas with lots of grass. You probably won't be hunting them out in the open during rifle season but they'll feed in the openings at night. Unbroken expanses of thick doghair timber just don't have enough feed to support large numbers of elk over the course of a year. Plus it's hard to locate elk in thick timber when they're not bugling and there's no snow, you have to walk right up on 'em. If they're sparse to begin with, you can do better somewhere else.
I switched hunting areas, actually tried a different part of the state and had better results right off the bat. Part of it was more parks and meadows with more feed and more animals, and part of it was the quality of the soils and the habitat. In the first areas I hunted the grass was short and sparse. In the areas I hunt now it's lush and waist height by the end of summer. No comparison in the quality of the feed and the number of animals it can support. You can see it in the trees too. One more clue to look for is the underlying bedrock. Soils that form over granite are generally thin, with low cation exchange capacity, low pH buffering, and low moisture capacity. Soils that form over sedimentary rocks, especially shale and limestone are thicker, richer, and hold more moisture and you can see the difference in the quality of vegetation that grows there, and the numbers of animals the habitat supports.
