Hero Manual Control

Every time I left-click a target, my entire party seems to rush that enemy. The only exception to this is when I call a target, in which case they stay on the called target first and foremost.

I know that, if I select a target and then click the cross-hair on my hero's panel that that's the only hero who will specifically target that one enemy, but I'm wondering if there's any easier way to go about it?

For example, is there any way to stop my whole party from swarming every time I change targets for myself (I frequently have my party occupy themselves with various minions while I harass healers, etc.)

In particular, one of my heroes - Koss - I have setup with a ton of knockdown skills, so I tend to have him repeatedly KD a target, but it quickly grows cumbersome when every time I select an enemy, everyone stops what they're doing and rushes that single mob (or worse, gets stuck on terrain/other characters and stands there doing nothing)

Basically, I'd like to be able to select an enemy by clicking but maintain 100% manual control over what everyone does. If I want the AI to attack someone, I've got my trusty spacebar for that.