In Dark Souls 1 there were several enemies that would commonly drop Humanity that were within a reasonable farming time. There are more than a few enemies in Dark Souls 2 that drop Effigies as well (essentially the same item). But in Dark Souls 2 enemies can only be killed 12 times before they disappear, meaning you only have 12 chances (sans Bonfire Ascetic) to kill anything and hope it drops something. So, while you might get a few it isn't nearly as much as you had access to in Dark Souls 1. This means you can cause your character to be permanently debilitated and get stuck behind a boss that you can't quite beat on your own.
So how can I farm (or buy) Effigy's or restore my humanity consistently?
Best Answer
Human Effigies can be found from Starting Gift, Static Locations (corpses), Merchants (All merchants have limited supply), and NPC's (both given and dropped when killed).
The term 'farm' usually implies an unlimited resource, as you pointed out. As of the latest patch, the Company of Champions covenant allows infinite respawn.
These are enemies that drop Effigies:
Always remember you can farm 6 effigies off of the Old Firekeepers and 3 alone off Housekeeper Milibeth in Things Betwixt.
There is however a way to restore humanity consistently.
There is an easier way, although it seems so easy that it will be patched.