The guild enforcer nerf is rough, but warranted. When aggro decks are playing a 5 cost 3/5 frontline creature, you know it's time to change it up a bit.
That being said I do think armor in general is very OP. It's an effect that stacks value every single time it's interacted with on a damage basis. The only true counter is hard removal.
I'm open to seeing how this nerf goes though, maybe it'll prove me wrong and armor isn't fundamentally broken, but we will see! I'm still keeping Guild enforcer in all my mid range and control decks until a better option to slow down aggro shows up though.