Brancrese
There's many problems with the loot system. But with weapons in particular, it's exceedingly bad.
Since loot is assigned when a cave spawns, not at death (confirmed by Gimli) this creates an issue since, at many times not everyone can clear an entire cave.
Now obviously the numbers are more complicated than this, but at it's face, the problem of loot gets exasperated by this issue:
If 100 mobs spawn in a cave, and there's a 1% chance for "x" loot to spawn on each mob. 1 of the mobs in that cave will have the loot. Now, if the person who spawned that cave, doesn't kill that 1 mob, they don't find the loot. There's a whole list of reasons someone wouldn't get to that mob. They could crash/DC (NETERR alert), their dog could jump on their lap and pull the power cord from the computer. They could get spouse/child aggro. Or maybe they just flat out get a bad spawn group and can't progress in the cave any further.
The list goes on. But now, a weapon, which hit it's (really low) chance to actually spawn, and should be added to the economy, is gone. This means you're essentially doubling down on the RNG metrics. The ideal solution would be to make loot pull at the time of mob death, not spawn. This way the chance to get it loot is static, certain mobs would obviously have higher chance. I don't know how practical this is with limitations in the code/client. But the point is, the way the system is right now is setup for failure.
Back to the weapons issue, all these issues with loot, are then amplified even further because, of those weapons that do drop, 50% of them are going to blow up. Because everyone is going to try and 4x a weapon. The problems with loot, when it comes to armor, are lessened, because people can just 2-3x their armor, so 30% less of those drops, turn to dust. Also everything is BoE, so of the drops that do survive this gauntlet, they're also now gone once someone equips them. So basically, this problem will never go away.
TLDNR: "Loot assigned at spawn" creates additional issues in the looting system. Also, since 50% of weapons blow up, weapon drop rates need to be substantially higher.