I did a quick search and found an Alton Brown recipe that looked similar, though it was for a cut-up chicken, not just thighs. With all due respect to AB, that sounds like a quick brine that probably shouldn't go for more than an hour. That aside, did you use kosher salt and did you measure it by volume or weigh it? If you weigh it, salt is salt, more or less. If you go by volume, you need to be careful because densities vary. According to an
article at Serious Eats, table salt weighs 10 oz. per cup, Morton kosher salt weighs 8 oz. per cup, and Diamond Crystal kosher salt weighs 5 oz. per cup. Given the volume and weight in the recipe I found, it was designed for Diamond Crystal. If you measured by volume and used Morton kosher salt you ended up with 6 oz. of salt rather than the intended 3.5 oz. If you used table salt, you got 7.5 oz. Either of these would explain why it seemed so salty.
Should you do it again, I would suggest weighing the salt to be sure you get the right brine concentration. I would also cut the brining time to no more than one hour.
Much of the food world has moved on from wet brining. Dry brining is now the "in" thing. It accomplishes the same goals as wet brining without sucking a lot of water into the meat. You rub salt on the surface of the meat and leave it to sit for various times depending on the type of meat and the cut. Excess salt is rinsed from the surface before cooking. The salt migrates to the inside of the meat and causes it to retain more of its natural moisture during cooking. Wet brining can result in a somewhat mushy texture. Dry brining avoids this.
Using all chicken thighs, I probably wouldn't brine in the first place. While the recipe called for a whole chicken, the brining is usually for the white meat. You have to seriously abuse a chicken thigh to overcook it to the point where it gets dry. I would just sprinkle the thighs with salt and pepper and whatever else you want to use in the rub.