Happens to me as well, a lot, but for me it is fixed when i loose my main's target and then retarget some mob (so just spam escape since the mob will likely be hitting on you and get himself as your target again)
this way during the charm i have 0 dps, but as soon as the charm is over i drop target, retarget, and it works again

the macro i use is:

#showtooltip Lightning Bolt
/use [target=Inner Demon, harm,nodead,exists][target=focustarget,harm][target=focustargettarget,harm][harm] Lightning Bolt

ignore the first inner demon thing, thats just for when I go SSC