You don't have to attack the ogre from behind to force Elbow Drop; you just need to be behind him with enmity. One time I was WHM doing that when everyone but the tank and I fell and I couldn't cast Raise. It was going well until Golden Week's server stress caused a connection drop.

However, I'm questioning if you even need to have enmity. With the way my log is set up I won't see skills used unless I have some level of enmity. One time I was just walking around and dodging by animation, no log messages. It's possible there was a mage too close, but I'm not sure. I think it's worth checking out, just to see.