Right. What I was trying to say is that I REEEEAAAAALLLLLY dont think that the Walkers are equivalent to Archangels. Mab or the Mothers, maybe, but not the sort of Trans-dimensional, outside-of-time being that Uriel is.
I think they might be equivalent to what Archangels are able to do on our plane of existence without breaking it. Sort of like how the Mothers don't leave the Nevernever because otherwise reality would warp around them like a gravity well.
What intrigues me is that Jim states that they have weird restrictions on when/where they can use their power. Maybe because it comes from Outside? Once they're here they can't use it to its full extent, which is why Harry was able to kick He Who Walks Before's ass so thoroughly. But Outside is a different reality altogether, and they can do all sorts of insane things.