An uncharacteristically fascinating blog post on the official Gearbox blog sheds some light on the loot drop system in Borderlands 2. It does get rather technical at some points, but nevertheless there are some interesting tidbits:
- If a weapon is dropped by a bog-standard enemy, the likelihood of it being a “Legendary” weapon is 1 in 10,000.
- The “Vault Hunter Relic” works by reducing the probability that a given item will be common (thus increasing the probability that it will be something rarer).
- Pistols are the most commonly dropped weapon, launchers the rarest.
- Each weapon type will only drop once you reach a particular level. For example shotguns don’t drop until level 5, launchers until level 10.
- Every item drop is completely random.
- If you’re low on health (or ammunition) the likelihood that you’ll receive a health (or ammo) drop increases.
- Contrary to popular belief, enemies actually drop less loot when there are more players in co-op. But because there are more enemies when there are more players, the overall amount of loot dropped is indeed higher (perhaps more interesting is that the reason this is done is to cut down on the amount of time players in co-op spend looting rather than actually playing the game).