[Will Chamberlin]"Does the V-Log L capabilities of the GH4 now negate the need for an external recorder like the Ninja Assassin?"
No. If you want/need an external recorder, V-log doesn't change that.
[Will Chamberlin]"I don't need over 30 minutes of recording so would the GH4 with the firmware update be a solid option for 4K video without having to splash extra for the GH4R and even MORE with the Atomos?"
My understanding is that the GH4R is just a GH4 with the V-log firmware pre-installed. You don't have to get everything all at once. Get the GH4 and do some shooting. If you want the V-log then add that. If you decide later that you want external recording, then buy the Ninja Assassin.
Just to add to why you might want a Ninja, it's really nice, depending on your assignment, to have a larger monitor to assist with focus. Not sure the Ninja Prores output is going to be "better" than the AVCHD or MOV internally, but having 500GB of storage to spool to is really a nice feature. I don't have to worry about running out of storage, and I often plug it in if I'm shooting an event.