I hadn't seen this mentioned anywhere, but as you rank up the Rise of Iron book and you get armor packages you can get an infinite number of them (one held at a time) that will roll differently each time at Armor 3.

I didn't see any changes to the gear perks, but the stat rolls would change. So if you like the look but are sad that you got Int/Str instead of Int/Dis, you can fix that for 3 legendary marks.

I'd been putting off picking them up, because I know I'll want to keep them but if the roll is garbage they'll just clog up space in my vault.

Oh wow, thanks! I hadn't thought to go back and look. This is great news because on my initial set, only the hunter arms really had stats/perks that were useful to me - the Warlock and Titan gear was meh. Which was a shame because I liked the look of the Titan arms.