The drop system used in most games these days is a rng system. Yes, there were games in the past that used a pattern drop system, but that was because rng was not really rng. It would use rng to determine a drop order when it started up.
On top of rng, D3 also uses weighted drop system. This means each item has a number assigned to it that is then used to determine its drop chance.
Say you have two items, one has a weight of 2 and the other a weight of one. You add those two numbers together and you get a total of 3.
1: Item 1
2: Item 1
3: Item 2
You have the game generate a number between 1 and 3 and what it lands on determines what is given. If you add another item with a weight of 3, then it looks like this:
1: Item 1
2: Item 1
3: Item 2
4: Item 3
5: Item 3
6: Item 3
So, do a random roll between 1 and 6, compare it to the table and you get the drop.
I, like some others, have a sinking suspicion that not all items are included in the weights, or their weights are changed. There used to be a spreadsheet that had all the official weights, but it does not seem to exist anymore. What makes the changing of weights more likely in my book is that they change weights for other class’s items and so, the tech exists.
If you want proof of this, I did a 7 item rare item run for mighty weapons. There are 8 of them and hence, if all are equal, they each would have a 12.5% chance to drop. Every time you go to get an item again, you have a 12.5% chance to get one. The chance to get a specific item in those 7 tries is 39.2%. To get a 90% chance to get the item you want, it will take:
1-(1/8) = (1-(90%/100))^1/n
0.875 = 0.1^1/n
n = 17.24
So, getting 3 of one item is a row is really suspicious. I do not know the statistical math to figure out the chance for that to happen. From what I have read, my suspicion is that it is is 1/24 or 4.2%. Do not take that with any certainty though.
So, yeah, I keep seeing things like this every day where somethings are coming out a lot more common then they should.
