Instead of bosses dropping specific items, they simply have a much higher chance to drop magical items. This means that while you can kill what you want and still have a chance to find something good, you aren’t able to farm the same few monsters over and over for the exact drop you want. You’ll also find a lot you can’t use, and that’s where the artisans and auction house come into play.
If you’re a WoW player, I think the closest thing to Diablo 3’s RNG are “world drops”, those rare items that can come from any creature in the world, but have a very low drop rate. This means that farming is done in a very different manner from other games – you generally don’t farm for one particular item or a group of items, you’re just trying to get rare, valuable equipment, plans, or commodities.
It’s worth noting that crafted items, in particular, suffer from RNG. When crafting an item, you are only given a general idea of what you’ll make – the attributes themselves are randomly determined. For example, if you craft a “Staff of Leetness” , it could have any combination of three affixes, stats, or attributes. This means that perfectly itemized items are excruciatingly rare, and thus worth incredibly large sums of Diablo 3 Gold. Most of the time, you’ll just make mediocre or poorly itemized weapons and armor. Don’t fret, however. At this point in time, poorly itemized equipment is still considered to be “okay”, and can actually command high prices. This is because, at the moment, crafters are hard to come by. If you’re interested in crafting, I recommend you read both my article on Crafting, as well as my in-depth Crafting Guide. Note, however, that it contains time-sensitive information.