You can't attack a charmed MOB as an enemy. Once it's charmed its considered a pet (like any of the other pets) and cannot be targeted for any damage by you or non-hostile PCs.
What you could do, however, would be find 4 ^^^ enemies close to eachother, Charm 3 of them, use those 3 to beat the living crap out of 1, then break 1 charm and beat the crap out that with 2, break 1 and have those 2 beat at eachother, break charm right before they both break and have chanters root them and nuke to death.
Then you do get both exp AND drops.
I've just gotten off my 11 Coercer (ran out of Vitality long ago and am getting tired) and I cannot believe the level of awesomeness that entails being a coercer. Not only is charm more powerful than EQ1, but it gives the enchanter a warning AND stuns the monster after the charm breaks. The way Root works in EQ2 also makes root'n'nuke not so effective, as root has increased chances of breaking early when you're casting on them (not so different from EQ1 actually) which has everyone always whining about how pointless root is. But rooting as a Psuedo-Mez means you can keep multiple monsters busy while your charmed pet can handle 1 at a time. So friggin powerful.
Just, obviously, gotta watchout for breakaways, because you do die pretty quick.
Oh, and I highly suggest coercers get Imbued Wands (the clicky ones)... cuz they are a mana-free way to deal a great deal of damage to assist your charmed pet.