I've found that later in the wow week (especially monday night) most pug leaders are more and more desperate, and will let anyone in. I've even seen specific "alt runs" where they simply want to know your own level of skill/experience just so they know how to fill out the raid, and to what extent they need to explain fights to people.

I've even got all 5 of my PvP geared shaman into a VoA 25 on a monday right after we took over WG, and all 5 of me got the achievement each time.... I even got an item for my resto offspec. I tried to do 5 of a 10 man, but they were trying to do Koralon with only one tank, and 2 healers, and needless to say, that it wasn't nearly enough, and theres so much movement required in that fight, my dps was severely gimped, and due to lack of healers, i was spammin chain heals during the mass aoe phase, so i ran oom rather quickly.