If you use Hate's Attraction, while the icon for the CPU will move to you,. you get 'too far away' to hit it. Sending in pets to attack it will result in the pets running to the starting location of the CPU.
Sending in just pets and ranged (spells), CPU started summoning first try at 20%. Later tries sending just pets resulted in summoning. Didn't have the right mercs to see what happened with a tank merc and a cleric merc, with all toons losing aggro through skills, etc.
Looks like time for CC or plan to burn the adds down.