Mmmm I really wouldn't call it an exploit. Those usually lead to harmful play, as in it has some sort of lasting effect that changes the one and only way you can accomplish something.

An example would be if fighting a mob in a certain spot of the area would cause it to no longer attack you until it dies, or be able to kite outside of its leash range. You'd be abusing a problem that was never intended to occur, ever. Infinite spawns are part of FATEs, it's kind of part of the system. You can sort of do this in lower level FATEs that involve something other than killing, such as the resource gathering ones (e.g. gobs outside Quarrymill), it's just not as effective... for various reasons.

DD, being how it is, isn't a problem. It's basically an old fashioned exp party for 15min. A good change of pace from the 45+ levels of generic FATE grinding.