I always hesitate to use words like "useless." But I agree, the volume on the steering wheel is not good. The big issue, I think, is the delay between pushing the knob up and the actual reaction in the software. If they can fix that delay, I think it would be fine. Continuing to hold it up will continue to increase volume just fine. The problem is that the delay causes you to hold it for too long, which then makes you overshoot the amount of change you wanted.
I think it can be fixed in software, though. It's odd, given the center rocker doesn't have a delay. And neither does the left steering wheel knob for controlling HA speed.