Okay, so it does appear that it was RivaTuner that was breaking the Capture with Final Fantasy XIV Online (ffxiv_dx11.exe).
With Open I was able to reproduce the problem, Exited RivaTuner and Attempted to hook and it still failed. Relaunched OBS still failed, relauched ffxiv_dx11.exe and OBS was immediately able to hook in. Relaunched RivaTuner Relaunched game and obs and it broke, no longer able to get OBS to hook.
I've tweaked the settings and so far I'm able to connect. Basically I just disable application detection and On-Screen Display Support for "Global" and this seems to have worked, I've done about 4 tests so far in both settings and it reliably doesn't work with the initial RivaTuner settings and Reliably works without those set. Thank you, for pointing me in that direction I was not finding it.
Initial RivaTuner Settings (Doesn't work):
Changed the Global to as follows (Works):
This suggest that when it was working was likely that I had OBS open before RivaTuner was able to setup it's hooks into the OS, allowing OBS to take precedent.