so why the change by relic?
Iirc, it says in the patchnotes I linked to you...
@Milkacow: I see. I was considering that armor+cover constitutes two rolls, whereas cover+acc red is a multiplicative single roll, perhaps to the result that it ends up scaling poorly according to the quality of the cover, whereas armor would be a single separate concrete roll in addition to first rolling past the cover modifier to hit.