All legendaries that you get from specific sources have the same drop rate. It’s roughly 1/10. The thing is that stuff like bloated loot pools will affect the actual chances of getting the legendary you’re looking for. Because of this, enemies that don’t have more than one unique item in their loot pool end up apparently coughing up their legendaries more often. Enemies that drop multiple legendaries have that 1/10 chance of dropping one of them, but it might not be the one you actually want. Still, the actual legendary drop rate remains exactly the same. Think of it like this: The item doesn’t actually have a 1/10 chance of dropping, it’s the enemy that has a 1/10 chance to drop one of his unique items. The only enemy that I can think of right now that has a different, fixed drop rate is Vermi. He actually has a 1/1 chance of dropping one of his uniques. Every time you kill him, he will drop one. But since he drops a lot of unique items, it might not be the Norfleet. The only case I’m not particularly certain if the drop rate is the same is the Longbow. That one might have a lower drop rate than the others, but I’m not entirely sure.