Well I guess this means I'm going to actually have to micromanage on my nightmare playthrough, sigh...that's going to be very dull. I hope atleast the AI is smart enough to detonate cross class combos, if not micromanaging will just become even more monotonous.
When have you never had to? Don't lie 
I always avoid using tactics on Nightmare (so every game ever). I would only use them for sustained abilities, intelligent potion use, and random single target abilities usage.
AOE spells (including every warrior attack ever and most upgraded spells) were a nightmare (get it?) to avoid getting hit by without having to manually use while moving your characters.
Now you can control when to use potions, when to stop using abilities, and when to use abilities... using a simplified interface that did the exact same thing you did before.
So frankly this new system changes nothing for me, and it shouldn't for most Hard/Nightmare players.
The tactics system was always excessive anyway. If you want to play real-time while your allies do their work automatically then push it down to Normal or Casual. It's nonsensical for that mode to be "nightmarish" anyway.