Most items that dropped could have 6 primary stats from a very large pool and 2 secondary stats (again from a large pool). The chances of getting something that was actually useful was very, very low.
For example - some item slots were designated combat slots and best used with a particular set of stats as they could roll no where else. (Crit chance / Crit damage / attack speed on rings, amulets, gloves) If the RNG gods did not favour you the item irrespective of other attributes was garbage. On top of that your character had a primary stat (str / dex / int) and if the item had its primary stat as something else (so you're a barbarian and the RNG gods gave you in effect a wizard item) again it was garbage.
To give you an idea of the numbers:
- To get a perfect item (Trifactor stats & 2 other useful ones) you would craft it once every 142,500 attempts.
- To get an item close to perfect (Trifactor stats & Armour) you would craft it once every 210 attempts.
- To get an item reasonable (just Trifactor) you would need to craft 110 items.
You see - Blizzard thought they were being smart but instead it just frustrated players immensely - the looting system in D3 was rubbish and you had to be very, very lucky to get something good otherwise 99.9% of all drops/crafts were garbage.
Blizzard took note and introduced SmartLoot 2.0 ... that meant most of the drops were at least designed for your character. Play as a barbarian and on the whole barbarian items dropped (taking care of 1 stat to be the correct type) That means more of the loot was appropriate but still RNG meant most of it was garbage.
That was primarily why Blizzard introduced the Mystic NPC who had the ability to take an item from you,
you selected a stat to reroll and for a fee would roll it through the RNG machine again. You could do this as many times as you liked but each time the cost was a little higher. This helped solve partially the problem so that a semi-perfect crafted item with 1 wrong stat could be rerolled and maybe that 1 wrong stat would come out good.