Alright seeing as Blizzard has nerfed or is most likely going to nerf the ToT farming spot I went on a search for a new location to farm charms. I found that the Stone bats of deep holm often drop the charms. Each bat has 5k health and they travel in packs of around 6-8. I would also suggest killing the packs of Jaspertip Swarmers that attack the rock guys. The Swarmers are in the same general areas of the bats and have 10k health and travel in group of 5+. This place is also helpful for anyone who was not able to solo the first boss in ToT
Stone bat - Stone Bat - NPC - World of Warcraft
Jaspertip Swarmers - Jaspertip Swarmer - NPC - World of Warcraft
I have not come up with a ratio yet but I can confidently say this is a hell of a lot better than any where in icecrown where charms are getting farmed like mad. When I was farming here I found absolutely zero people here except 1 person who was questing.
Just follow the spawn locations on this map:
TIPS:
1) I believe that if you have not completed the questline in deepholm the rock guys with 500k hp will attack you.
2) Turn on enemy name plates so you can see their yellow health bars(Default key bind is v)