EDIT:
Ignore me, I see you have some sort of vertical offset thing.
You should have used it - stop me from looking like an idiot.
This is all done on a terrain though. If that terrain was meant to be mountainous, then in the first picture, the AI has just Larged itself right through the Alps, when it probably should have gone around it - assuming the player is a pin-point on that terrain.
You go on to discuss rooms which is going to be pretty much a flat terrain and nothing to do with this concept, which is where some people will think about NavMeshes.
I don't see any mention of gradient being stored in your nodes, but the images clearly show that they are being laid down in 3D. With that added, then it is easy for the AI to accurately work out the best route - ie, it doesn't try to walk down a sheer cliff or something - plus it means that your logic will be faster as, with this type of terrain (depending on scale), you can kill of a whole bunch of connections. For flattish terrain then it wouldn't be required.
You'll know when it is right when you have the same screenshots, but with a whole bunch of those nodes coloured red, for example, (after you add in the gradients), and you will then have actual walkable routes which can dynamically change as you alter the scale of the terrain - in a nutshell, your whole grid will modify to the terrain. All you add in is additional rules based on gradients, which can all be done from a master control which can be independent to whatever you like - ie a certain vehicle can handle a wider range of gradients, etc.