I was charming these with my druid and it seemed as if they never cast their dot on the mob he and I were fighting (Other gorillas), yet my charmed mob was always dotted by the mob. I could always count on the other mob to beat the coconut out of my charmed one and then I'd have to charm the other one in order to kill the one low on HP.
It was not even close with me adding a single dot to the fight. Sorry, not many dots memmed when I'm charming.
So just a little warning.
This might be normal in the game now, but its been a while since I charmed animals and I was not expecting it.