People will _ALWAYS_ find the path of least resistance to level as quickly as they can. This is the current method. If it is deemed to be an "exploit", which it is not, then people will find the next fastest and spam that instead.

Trying to FORCE people to do varied content is absolutely ridiculous; some people will always use the fastest method.

As for the practice in question; these are mobs in a game world that also happen to be in a perfect place when there ISN'T a fate going on for grinding for a number of reasons; not the least of which is spiritbonding gear. The players aren't doing anything to force the exploit, and in order to NOT do it they would have to simply stop killing the mobs, which makes no sense. This is NOT an exploit. It may be a bad design issue, which SE will change if they feel it worthwhile, but it is not an exploit.