As I understand it, the reason for the repeat penalty is so that people will buy more packs. If they can buy one pack and run it endlessly, they might not buy other packs.
If that is the case, why not let VIP's (who have access to all packs) be exempt from repeat penalties for XP?
If, however, the reason for XP repeat penalties is NOT to encourage people to buy more packs, what is the reason? The "get people to buy packs" is the only reason I've heard that makes sense, but it is certainly possible there's another reason.
I don't really see why Turbine would care if a VIP runs Gianthold quests a few dozen times while ignoring Necropolis quests (for example.) I'm sure there are at least as many fans of the Necropolis quests as there are people who don't like them, so there would still be parties forming (except for maybe Tomb of the Tormented...)