Charm kiting is less...eh...fruitful than swarm-kiting, because if you can kill hundreds of mobs in 30 minutes instead of two mobs every 5 minutes, why go charm kiting? Not everyone who plays a bard is into mass genocide, it's just the most interesting thing bards can do so you get a lot of video of it.
As for bards in groups doing it, they're usually twisting a bunch of songs for other purposes and having a charmed pet break and beat on them is more trouble than it's worth most of the time. Plus, charm spells do use mana for bards.
You can actually charm kite and swarm kite at the same time. I haven't done that myself but I did find a guide on that very thing on the forums.
The most famous bard charm kiting incident is actually with Fansy the Famous Bard
[You must be logged in to view images. Log in or Register.] He charmed an NPC that the Priest of Discord would assist and sent the pet to kill players so the PoD would murder them in Rivervale. It was highly effective!