The BEST place to farm Lovely Charms: Halls of Lightning normal mode; The Slagpit

Also, for everyone going to farm them: The Lovely Charms stack to 40, but the Bracelets don't stack at all, so don't combine the Charms until you're ready to turn them in.

I like to go clear the 3 ICC dungeons, chance at Battered Hilt, and a few hundred tokens (I use it to farm the 250 grizzly trophies mostly, have yet to start the charm bracelets) and I usually do it in one day, with the bracelets I may do it more often, and possibly try Slagpit, or Molten Front seems like a good idea.

Another great place is Throne of the Tides. Kill first boss then sit on that corridor before the last boss (don't kill last two adds at the door) and kill the little oozes over and over again without having to ever move. 0 Downtime, lots of them and best of all only 1 aoe skill to kill them all.