Don't tighten your lock rings so tight. Half the time I don't need a chain whip to loosen mine. Just a rag to keep the teeth from sticking me when I hold the cassette.
The cheap tool is fine if it isn't slipping. If you aren't doing this every day of your life a better tool will just be something to brag about.
Not sure why you didn't put a cheater over the hex wrench if it is that tight.