1170 is not low for Mag but is easy and inexpensive to adjust. IO used to be low on calcium and mag, so I would mix it 50/50 with Oceanic, which was high in calcium and mag, then they upped the calcium and mag in IO and I no longer had to do that. Just about every salt out there has had consistency issues from time to time but that isn't a big deal if you adjust your change water to the parameters of your tank. FWIW I have never had a bad batch of salt, but I suppose it can happen. I have been using just IO for several years and it has mixed fairly consistent, well within the testing limits of our hobby test kits. The "designer" salts don't really have anything you need but do have a higher cost which seems silly to me. Some of the best tanks out there are running IO so it kind of negates the need for the high priced salts. RC has added vitamins and EDTA which doesn't do anything for the tank, has a tendency to mix up with the brown sludge which doesn't seem to cause harm.
The salt debates that have happened over the years are amusing, it is so easy to adjust your salt to the tank parameters if needed. ESV seems to be one that is mixing consistent for many people and I suppose that makes it worth it to some, nothing wrong with that. I dose the tank with what is needed because water changes could never keep up with the tank's needs, so any minor corrections to change water is easy. With IO I rarely have to adjust anything, and small water changes don't change the tank parameters by much so if I do a small one then I don't adjust it at all. I haven't touched reef crystals in many years, haven't had the need.
The salt debates that have happened over the years are amusing, it is so easy to adjust your salt to the tank parameters if needed. ESV seems to be one that is mixing consistent for many people and I suppose that makes it worth it to some, nothing wrong with that. I dose the tank with what is needed because water changes could never keep up with the tank's needs, so any minor corrections to change water is easy. With IO I rarely have to adjust anything, and small water changes don't change the tank parameters by much so if I do a small one then I don't adjust it at all. I haven't touched reef crystals in many years, haven't had the need.