As a brief refresher, diminishing returns causes spell effects such as Fear or Root, when used against enemy players or specially flagged creatures, to have reduced effectiveness after each successive cast. In The War Within, the first Fear cast on you will have 100% of expected duration, the second will have 50% of expected duration, the third will have 25% of expected duration, and then you become immune.
In Midnight, the diminishing returns for these spells will now go from 100% duration to 50% duration, to immune. We have also reduced the amount of time for diminishing returns to reset itself from 18 seconds to 16 seconds.
So right now it’s: 100% → 50% → 25% → 0%
It’ll be: 100% → 50% → 0%
That’s a nerf, and 18s-16s before a full reset changes almost nothing, since it was interrupt rather than the stun/fear/whatever that we wanted in the first place. So not only do we have less interrupts, CC is now less effective at stopping as well. It’s a lose lose!
All that’ll mean is that the outlier CC will be more desirable, which means an even more restrictive meta.