Well I'm in OT by FM ledge charming there. What it is, is not so much I can't charm them, I'm just finding myself after 2 mobs I'm out of mana.
Ishio
Here's what I do. I ensnare two mobs, get them close, charm the animal, sic him on the other snared pet, let them fight to 20%, or one to 20%, cameo, nuke. I recharm if my pet is still okay, ensnare another and repeat. On the second repeat, though I am medding while the pets are fighting, I'm out of mana by the third ensnare cast.
I have about 1.3k mana and I'm just drained. So by the time I need to kill pet and second mob grabbed, I'm kiting them while I'm waiting for my dot to kill them. Yes, I know that dots don't do full damage when mobs are moving, but I get them to 10% and they've regened enough health to move again while I med to try and kill them.