Interesting replies to course difficulty. When I think of the future of these dogs and the future of using them to help on a stock farm, I can't help but think in a trial context, as this is how I entered into the examination of the interaction between dog and sheep (helped or hindered by a handler) which is "herding" as It is today.
We speak of breeding decisions for the "improvement" of the breed, and also with great fondness for the dogs of the past as well as the ways of living which created them. An interesting balance.
If there is a course "standard", in which the grass is neither too tall nor too short, the sheep are wild, fresh, workable and healthy, as well as agreeable and dependable with a particular fondness for the pen but not so much for each other that they won't shed, the hills are not too high to scale, nor low--can't see the dog, the outrun is huge and impressive but not too far, the sheep are well held on a beautiful day, do we breed to "this" standard?
I'm teasing a bit but I do think the art of this thing we love is this sort of balancing act.
I think there is room in this activity for the occasional merle--know a couple really cute ones that get the job done quite well HERE IN THE UPPER MIDWEST, where there are all kinds of trials and all sorts of sheep.