1) Are you using Deathchill and Ravages? If so I think if you get to close the monsters with the auras up, they'll draw aggro to you. Because they're considered an attack. I may be wrong about that but someone will correct me.
2) The first time I used it was with a hybrid bow/spear Slayer and it took a couple of tries for me to get far enough away for the monsters to target it. More than likely you can take all the points from Detonate and all but one from ML and put them some where else that they'll do you more good. Plus, when you get +skills you can basically have a five point ML.