It is possible that these mobs are simply dropping generic rings. The mobs pull from more than one loot table and that is why you will often find random non-magical items on their corpses such as skulls, candles, lockpicks, lanterns, etc.
If the ring that you received does not have any magical properties and is using the new loot naming convention or has an item property listed in the tooltips like <Type> Magic Item, then there might be a problem with the loot.
If this is the case, can you please provide what type of magic item it is (legendary artifact, minor magic, etc.).
Thanks.