I've yet to see it, but Im on a pve server, the guards hit like trucks. I accidentally flew into the Alliance shrine autopiloting on my horde toon and was glad for bubble hearth glyph Lol
When I kited Kal'tik the Blight to the Shrine of 7 Stars and 2 guards came to attack him he went from 2.2mil hp down to less than 200k in only like 5 seconds, he only survived by killing the guards (and 2 nearby sitting AFK players) with his Blade Flurry. No player assisted him during that time. Was on a PVE server though.
So I doubt that even a 40man raid would stand a chance to last for long trying to raid the place on a PVE server, as that would spawn many more guards than just 2.