OK, so you can take a four-step approach here.
First, I would start with the pad. It's the cheapest way to start and I think it is the most direct. You need to make sure that the materials in your braking system are built to operate in the environment in which they are subjected. If your stock pads work efficiently from temperatures x degrees to x+500, and you are operating them at x+600, then you are using the wrong pads. Buy a compound that is designed to operate in, say, x+200 degrees to x+1000. What I am saying here, is that you are exceeding the temperature range of your pads.
More information on that: Yours are designed as "street / track" pads which means they are designed to work without warming up and that their temperature range is somewhere below freezing to several hundred degrees. This makes them ideal for driving on the street and autocross duty. I would start by finding a more aggressive compound. Be careful though. You may require track only pads, which I recommend, but you CANNOT drive with these on the street and you MUST warm them up before they work. Track pads alone may solve all of your overheating problems.
Second, you may wish to consider slotted rotors. They probably won't solve the fade issue by themselves though because while they may evacuate gas from between the surfaces, your pads will still be blazing hot and won't be as effective. Most racers I have encountered, including late 1990s Mustang GT endurance racers, use blank rotors (not slotted, not drilled). But if the pads alone aren't enough, this could help you. I use these weird-o ATE slotted rotors on my Miata that have some weird elliptical shapes slotted into them, but I really bought them because they had a really nice anti-rust coating on them. And they were affordable. I had fade issues just like you even with those rotors, until I went to my more aggressive compound.
Third, it seems as if you already have cool air being fed to your current setup. You might, if all else fails, consider running better air ducts to your brakes, but I am hesitant on this because I don't have any experience with it. Rapidly heating and then cooling steel can make it weaker. I think a rotor failure on a car is the scariest thing that can happen on a track. Seek professional help on this one before you make any changes.
Finally, and this should have been my first point, try racing slower. This can be facilitated by trading your Viper for my Miata. The Miata is nice and slow and doesn't have any braking issues, no matter how hard I try to make them fade. It's also a roadster, which is nice. When it rains at the track, it cools you off because many organizations won't let you run with your top up unless you have a hard top. It also has flip-up headlights. I'm just sayin'...
I should mention that the compound I went with is aggressive enough that street tires cannot fade them on the track, but they are streetable. But any more aggressive and they couldn't be used on the street. Race tires will exceed their capacity though, and I will be forced to move to a track-only pad which has to be warmed up first when I start putting race tires on it. They might be Hawk HT-10s, but I don't remember. If you do find a pad that is super aggressive, though, be prepared for it to be noisy and dusty.
I think you described my problem and solution and I really appreciate that. 
