This is a really neat and unique exotic weapon. It's fun to use and can be useful in all sorts of cheese. However, with it being in the Primary slot, that greatly limits the amounts of useful loadouts that it can synergise with. It is first and foremost a sidearm: as in a backup weapon. In many cases you will end up wielding your energy weapon as a backup. So if you have rat king, then you're sort of running two backup weapons. Rat king can be used like a primary, but it doesn't really feel like one entirely... unless you've got others wielding it together, which I guess is the point of it. But my point is that I feel it should be moved to the energy slot to allow loadouts to synergise with it better and actually allow it to fulfill the sidearm role that it actually is.