The air charge system, or strato charged feature, has NOTHING to do with the fuel mix, which is still entirely the job of carb. Some dealers don't understand strato, so in their minds it's "voodoo" and they tell everybody to stay away from it. Either he needs to warm up to this new technology, or he has to get out of the saw business, because they will all be that way before long. Strato is just a clean air pulse to reduce the amount of unburned intake charge blowing out of the muffler as on traditional two strokes. The strato charging is done through transfer ports, so it cannot go out of adjustment.
The 576 has a lot of changes from the 575, including carb, piston and cylinder, crank. There is no reason to stay away from it. All saws are set very lean from the factory, and a dealer that knows how they work will richen up the settings, without altering the limiter caps before it goes out.
That being said, I totally agree that the 372/2171 is probably the best family of saws that Husky has ever made, and I'd grab one while they are still available. They are as proven and reliable as you can get.