No order is right, in my opinion. However, I think that compressor placement (and even Wah for that matter) make a difference in the chain. Not that there is a right way. Since I found Wah's to have some level of compression-like qualities, I felt it was better after the OD. If it was before, I felt the tone was rather anemic since the OD was not getting fed the full bandwidth of signal. My old set up, I had the Wah on full time, pedal flat position (no, not the Schenker-kick back position...) because it tightened up the overdrive from the Boss Turbo OD I used. Even though it brightened the sound, with a little extra leaning on the Bass frequencies on the Amp tone, it had a really good sound.

So, no theory but how my stuff just sounded better. That also matters, no one set of equipment is the same so no signal path is really right or wrong.