Like everything else, there isn't one 'silver bullet' - pile of stresses on wildlife and sheep including psoroptes. Over-grazing up top is a known issue.
The fencing exclosures and plots are the best places to check if interested - not sure if they're even being monitored now. You could call the range or parks branch.
Alternatively you can compare the grass on either side of the fence above south slopes, or ask the outfitter (he packs feed in), or cut a horse loose up top and see if you can find 'em in the AM if you're into the anecdotal.
Again, evidence is probably the best thing for discussion.
So far as "Cows been there more then a hundred and fifty years and you can still hunt sheep..think about that." There will likely be two tags in the whole ashnola (both snowy and crater combined) next year. Wouldn't at all be surprised if it was closed. Certainly isn't all about grazing, pile of stresses on sheep in that country, grazing is but one.