guitarhack,
i've experienced these same fizzy results with my setup as well, ive reamped with a firepod, 6505 and into a my line 6 spider valve(same size as traditional cab with v30) and i also have the mesa os cab to compare with.
your clip sounds a lot like my clips with just a 57, but i find that you can get away from the fizz considerably when find the right mics to work against each other.
but here is probably a very important factor if not the most, yeah you can kind of guess at your phase alignment, but ive learned for huge tones espcially hi gain tones that we love so much, is that getting a perfect phase alignment is crucial with the right mics, when i mean perfect i mean actaully zooming in on your tracks in your daw and checking with a microscope and seeing if they are the same. getting multiple mics working together, like your 57+57, 57+421 is what you need sometimes, single mics doesnt seem to cut it for taming fizz(not always, just when the amp/cab is considerably fizzy), when using multiple mics, the goal with higain tones is to use one core mic for the bulk of the tone, then the 2nd mic can either reinforce or cancel out stuff, so you can essentially mask the fizz by canceling it out, much better than using an eq.
lets just say to get this right is a fucking pain in the ass, ive yelled and nearly back hand slapped people who knocked a positioned mic, because they just ruined 30 mins of setup for 1 mic.
have your tried the white noise technique?