I think the linear dungeons removed players who actually NEED XP from experiencing griefing if they ask for a "full clear". Imagine a DPS sitting in queue for 25+m and getting a track star tank who wants in and out?

At least with the linear dungeons, all the XP that is available in the instance can't be avoided...for the most part. God forbid you wake a slumbering Dragon in The Aery and it's like you just ruined some orphan's first Christmas...