The trouble with charm is it has to be carefully balanced, who likes to lose control of their character and be ganked?
The flip side of the balance is that it can become useless "fluff" very easily if it is underpowered. Sadly Sigil have not really released any details of PvP yet so it is difficult to say, though first thing would be to determine if any class can charm at all.
All we
do know is that PvP will be in after release and will be balanced seperately from PvE.