After running the daily heroic yesterday, one of my guildies gets the idea that we should PUG 25-man Ony. "Sure," I say, "get us into a group." Before I know it, we've formed a group, and had 24 people ready to storm Onyxia's Lair. (Yeah, not sure how we didn't get a 25th, but whatever.)
Like I said, it was mostly a PUG run. I knew none of these people except for my 1 guildie, and an ex-guildie (good friend).
And... the result: We one-shotted her.
Much like the 10-man version, the hard part was Phase 2. But once we got to Phase 3... even with about half the raid dead, it was still a pretty easy kill. I guess it just goes to show that some bosses can be very easy if people know what they're doing.