Have been goofing around with my 100% reduced cost Restoration magic and wanted to go beyond the free health spells. So I've been trying Circle of Protection and as I expected, it didn't work at all on the undead I've been facing cause they are too high level now (my mage is already quite advanced).

What I didn't expect though was that undeads inside the Circle somehow become impossible to stagger with Impact dual casted destruction spells. I didn't test that yet against non undeads but for sure it was a weird and painful thing to learn XD

There's many other things to try for that but I don't have the builds for it though

Do you have the Dual-Casting Restoration perk? Circle of Protection might give you better results if dual-cast. Still, I doubt that it should grant stagger protection.

No I don't but I wasn't exactly worrying about it not working that late in the game. It's more about the strange stagger (and what else?) protection undeads inside received.