I completely understand why they did it, from a server stability standpoint.
However, there will always be those that rush to they finish just to say they have a 50 or for their own fulfillment. Nerfing AE xp will either make it so they try harder with AE or find another way.
However however... until there is a sense of permanence in regards to the servers, the feeling of "oh crap I need to get to 50 so I can do X before it gets wiped/taken down" will be there for most people, which grows the farming base from a small group to a larger one.
And let's face it, even if the people running the servers come out and say they'll never wipe the severs ever again, the sword of Damocles that is NCSoft will always hang over our heads.