@frog Reaver - I'd say that tracking information like this will tell you rather a lot about that specific group.  Tracking across various campaigns will tell you even more about that specific group.  See, to me, I don't care about any else's group.  I've seen far too many "Oh this is broken" or "5e is D&D on easy mode" type arguments to think that what happens at someone else's table even remotely resembles what happens at mine.
Theorycrafting assumes too much.  Sure, it's a great start to give you a direction for what you need to look at, but, by and large, I find theorycrafting very pointless.  It simply will not predict what happens.
But, I totally agree that a single encounter or even a single day will tell you anything useful.  I did say that you should track about 20 rounds of combat.  More if you like.  I find 20 to be decent enough that it shows general trends.  But, absolutely it's only showing general trends for that specific group.
But, trends for a specific group is far, far more useful to that group than theorycrafting which tries to make general statements based on nothing more than hypotheticals.  I mean, heck, you talk about 300 foot darkvision being an issue. 
Why?  IME, it's almost impossible for encounters at that range.  There's never sight lines out that far, for one.  For another, I almost never see any combat starting at that kind of range unless maybe the PC's were deliberately hunting something.  I can't imagine that actually having any impact at my table.  It just wouldn't.  But, OTOH, at other tables, maybe it would.  
Again, that's why I'm such a big proponent of empirical evidence over theory.