Guild runs in dungeons are always easier than PUG's because guildies tend to know each other and won't act like an idiot - they'll actually try to learn the dungeon so the group is successful.
It's why coordinated groups tend to win in PVP as well .
Funny to see this in trade chat yesterday:
Question: "Why can't we [alliance] win TB yet we dominated in WG [Wintergrasp]?"
Answer: "Because in WG we could easily outnumber the horde, in TB - we can't"
Same thing happened in AB and WSG - unless it was a purposely built to win PVP alliance group, the horde would easily steamroll Alliance most of the time.
Alliance on the server I'm on are very good at PVE [which makes sense since it's a PVE server], yet most suck or dislike PVP.
I haven't healbotted or dps'd in any dungeon yet - but I suspect it's pretty much the same mess I saw in WOTLK until people were geared and knew the dungeons.