I have recently bought Destiny, and I have noticed that I seem to acquire many duplicate items. For example, I have three Firebreak helmets (however one of them is Firebreak Type 4), and I also acquired three Trax Callum I scout rifles, (although I have dismantled two of them). However, each of these items says that they unlock at different levels and have different attack powers/defense points, even though they are the same thing. Is this a bug, or is this normal?
In Destiny, all of the weapons and armor are randomly generated except for Legendary and Exotic equipment. Generally the higher the level requirement, the better the stats that are rolled for your equipment. Legendary and exotic equipment will actually have unique names/stats that are the same for multiple copies of the same piece.
This is completely normal, and part of the "Destiny" way of doing loot drops.
Perfectly normal! :)
Green and blue items will roll very similar names and stats all the time. Mangala Skin... always, I always find these on my hunter even at level 32. The first google result for Mangala skin is a reddit post titled "I hate Mangala Skin" (I can relate).
Legendaries and Exotics are a different story.
All exotic weapons of the same name are exactly the same (aside from ones from different expansion versions).
All raid obtained legendary weapons of the same name are exactly the same.
All exotic armor of the same name have the same benefits, but their stats can differ.
All legendary armor of the same name will be slightly different in both its benefits and stats.
All legendary weapons of the same name not obtained from a raid will be slightly different in benefits (Glass Half Full for example) but its stats will be exactly the same (Impact level, rate of fire, etc.).
Random, except legendary and exotic. Based on level, Grimoire rank and chosen difficulty probably. I will say though the Up for Anything legendary auto-rifle I missed and picked up at the postmaster has different stats than the vendor. I don't mean benefits, the vendor's is less stable and some less pronounced differences, same damage though. I don't think stability is part of its benefits.