So what next? Well, right now I'm using my old-as-dirt Tektronix 466 oscilloscope to take a peek at the chip enable signal from the micro controller and the resulting interrupt from the transceiver. Right off the bat I did notice that for every ping I was attempting I was actually send two... oops. Turns out that bringing the chip enable pin low as late as I was triggered the transceiver to transmit again once the interrupt was acknowledged. Bit of a waste of power and resources... and it'd also explain why the delay time between pings was suddenly important when it hadn't been previously. Moving the command to bring the chip enable back low a little earlier in code fixed that problem.
At this point I'm focusing on when I'm receiving the interrupt and how accurate the micro-controller is at measuring it. In my results I got a lot of erroneous results that were roughly 100-500 cycles later than others; an amount of variance I shouldn't be seeing. Through using the scope I can narrow it down to either the transceiver, micro controller, or potentially interference in the wiring (which I don't see right now). Time will tell!