If the stuff corresponds to your class, you can Need it.

There's no need to debate "rules" when the game has already laid them out for us. Don't like other people Needing "your" stuff? Play on the corresponding class, so you can Need it too. All there really is to it. The people who complain about this system being "unfair" are usually just the ones who think they're entitled to the loot. Hypocrisy much?

Personally speaking, if my *only* intent for a piece of gear is to hand it in for GC seals, I'll only Greed it instead. For any other purpose, I'll Need it instead if I can. But that's just how I roll personally; anyone else can literally Need every possible thing the game lets them Need, and that's totally up to them and within their rights because that's how the game works.