From a GM perspective, any changes, once made live, you should announce them, a) because if you don't announce the small changes, they slowly build up making a big difference, and people also can see you are actively working on the game still.
You might have made 50+ small changes in the background, but if people only see you nerfing things they will get their backs up.
Also with regards to changing EXP in areas after people have already taken advantage of it, is haunting, I think it's better to just manage other areas to make them also worth while to hunt in, (unless it was THAT broken, then why wasn't it flagged in BETA)