I had the same problem with excessive rust despite softening, to the
point we couldn't even drink the water. I had to install (well, I
didn't do it personally) a potassium permanganate unit. It looks like,
and takes up about the same amount of space as, a water softener.
Instead of a tank with salt, it has a tank about 1/4 the size to which
the potassium permanganate is added. It works very well and is
actually less hassle than the water softener, since the potassium
permanganate comes in a handy little bottle rather than gigantic, heavy
bags, like salt. It cost me a little over $300 to buy and have it
installed, and looks like a simple installation (i.e., someone more
knowledgeable than I might be able to do it without hiring a pro).
Note skull and crossbones all over the bottle of potassium permanganate
and keep in a safe place.