While I agree the physics of the SRV are hilariously broken (seriously, I tend to spend more time laughing at my SRV than driving it), you have to remember that you're driving on a barren planet. It's covered in particulate finer than sand. It's not a question of downward thrust or drive distribution, there's simply a complete lack of friction and therefore traction.
Would it be a nicer experience if the SRV handling was better? Absolutely. Would it be more realistic? No.
If you're having trouble getting around planets, I recommend accepting that the SRV is a better ship than car. Find a direction on the scanner, throttle up, and launch off an incline. Then use your vertical thrusters to stay airborne. I spend about 1/3 of my time on planets driving the SRV, rest is spent flying the thing.