I never got any of the full 10 piece sets of armor in any of the fortresses, always 9 pieces even when consulting a walkthrough for the locations.
They require a ridiculous number in a certain stat anyways and I was never even close with any of them. Last pieces I found were the scorpion pieces and I believe those took 42 dexterity or something to equip and I was around 35 and below 30 after I'd take my charmed or enchanted pieces away.
So the point is I never got to see if any of those pieces from any of the three sets were even worthwhile searching for as I could not put on one piece of the various.
I just used my Unique set I got off that one demon from the time I got till the end of game. Never found anything better for my particular character. Just enchanted and charmed it up better when I could.
Heck did not even sell the pieces, they were sitting in my battle tower chest when I finished the game. Not even sure if they were worth a good amount of gold or not.