The best spot i've found is the Tomb.I go there all the time and have at least 1 stack when I leave.Course I've gotta agree that i never gotten them offa Ding Bats.Most of the Time deeper in.Also good place for Bone Chips(for all you up and comming Bonecrafters^_^)
I got a half a stack of bat fangs casualy killing Mouse Bats in King Ranperre's Tomb with my lvl 24 DRK. I was in there to get the water for the Sandy quest "Grave Concerns", stopping along the way to kill bats.
I need several stacks of bat fangs and not only is the price high on these now (5K a stack on my server), but there are none up for sale at the AH. I'd be farming with my lvl 39 THF. So far I've tried the Inner Horrutoru Ruins (killing both single bat families and the '3' bat families) and, while I've gotten over 3 stacks of bat wings, I have not gotten a single bat fang.
I think groups might only drop wings and the singles only fangs, although I might have gotten wings off of them too. I agree I've never seen this drop from 3 bat groups.
go to the tomb go tru the first tunnel and come out to the next little maze area were the gravestone it wait till it is dark and kill the ding bats there much easyer to kill if your a low level doing this quest. I always get scales off these guys, i have never gotton one of a mouse bat in the cave...
[b][/b]Ok, if you are doing the Bat hunt for the second time this is what you need. In order to get it you have to hunt the omouse bats inside the caves. The have a pretty rare drop because i was in the cave for 2 hours and recieved only one... Also on a very rare occasion Mouse bats in South San'Dorian Forest they will drop Fangs too but i'm not sure if it will complete the mission.