I hunted the Nile Unit last year and any call made the elk head into the Bumping Area, You just couldn't call and expect to see any critters. South Fork Meadow years ago bulls were always bugling and cows and calves chirping.
I think there are two important factors at work here: Sometimes calls work, sometimes they don't and I think the more we know about the herds we are hunting, the more likely we will see and work critters. the important factor is in knowing which phase of the season the animals are Staging, pre-rut, rut, post rut. Each of these will have their own most successful tactics. The second and perhaps MOST IMPORTANT OF ALL

. . . DO NOT DISTURBE THEM IN THEIR BEDDING AREAS

. Doing so only guarantees that they are heading for the next county!