When a rear wheel drive car makes 1 tire revolution while driving how many revolutions does your drive shaft make?
It depends on the gearing in the differential. If the gear ratio is 3.42:1, the driveshaft will make 3.42 turns for every 1 turn of the wheel.
Are driveshafts mistaken as an off balanced tire if they are near the same ratio?
It could be, but unless you've done something to your driveshaft, this rarely happens. Usually, when working on vehicles, if you have a problem which occurred after doing some kind of work, you need to look at the work you did to find the issue. Very rarely is the problem outside of the scope of your work.
When does having a lessor and greater then ratios from tire to drive shaft matter?
The gear ratio is needed for either greater speed or greater torque. If you want greater top end speed, you use a numerically lower gear ratio (2.90:1 vs 4.11:1). If you want greater torque multiplication, you use a numerically higher gear ratio.