To many it seems like they always get gear they don't need and this is true because statistically as you gain more gear, the likelihood you'll receive what you're looking for gets smaller. Let me give you an example using apples. Red apples are your role gear. Yellow apples are your off role. Green is everything else. Now, put ten apples in a bag. Two red, two yellow, four green. All roles covered, yes? The two extra apples are just random variables. You may or may not find them useful. For kicks, lets throw in 5 oranges to represent plans and more random things or junk drops. So we have 15 items in the bag. Every time you get two-three items on average. Could be more. Now, every time you get a red or yellow (useable piece), mark it with an X. You can't equip the same piece twice. Every time you take out two apples, mark the useful piece, and put them back in the bag...just because we got the item, the loot table doesn't know that, so it's always fresh! If you follow this logic and example, you can see how it gets harder to obtain useful pieces you don't already have. I know this is simplistic, but I hope it helps.