Keep your RPMs modest before you launch. Of course you'll burn rubber for ten minutes if you launch at full throttle at 8k RPM haha. I just keep the revs low enough to spin just a bit, but then quickly catch. If you start out too low, you'll lose a lot of time coming off the line. Like others said, use wide drag slicks too.
I live on Forza 4. Message me if you'd like to race. Gamertag = JohnHance
As said above, launch at a reasonable RPM like you would in real life. I usually launch at around 3,000RPM and just control the throttle a bit. Ease it until it hits second, then smash the throttle.
With drag slicks and wide tires I don't get too much wheel spin even without tuning. I'm not sure how to tune that well for drag. But lower your rear tire pressure.
I think (don't quote me on this) in order to get grip at the rear you stiffen your front suspension and loosen your rear so the weight of the car is on the back wheels. This combined with drag slicks and wide tires, along with proper launching technique should get you your desired results.
2) Yes drag racing is STILL broken. There are tires out there that dont slip like this even with some heavy horsepower cars...they fixed it a little bit from F3 but still you should be able to have the tools to get your 500-600-700HP vehicle to hook up without AWD. Also there is no reason why the car should have some countdown and still be revving...please Turn10, set up drag racing like it is in real life, not imaginary land.
Anyway yea, wider tires, drag radials, lower the tire pressure and launch with care...