I honestly can't believe this is even a debate. There are pretty much no drawbacks to scaling with the dungeon. It is more fun and challenging. There is a greater sense of accomplishment. It gives an additional dungeon to actually do. The thing I'm worried about if there is no scaling is if the mobs will even aggro. Imagine just walking through the low level mobs straight to the boss. That would be terribly boring.

The question then becomes which is better- The mobs scaling up to make it difficult for R50's or The R50's scaling down to the appropriate level of the mobs?