If your fork locks out, then your oil levels are correct.
You are right, too coarse an adjustment for rebound or compression becomes useless on the trail.eatdrinkride said:Common complaint with new users. The fork really needs to be put through it's paces for the circuits to take affect. Early forks which started being supplied with compression settings were very obvious. You could make a change and tell the difference by pushing down on the fork. These systems made for a pretty useless adjustment when bombing hard as they were overly sensitive.........but buyers were happy b/c they could easily tell the difference in changes of settings.
Dial the damping all the way down and drop 2 or 3 feet to flat, then dial it up and see if it makes the bike more compliant and not just blast through it's travel. You could do some big roll offs that push the limit of the fork as well. That might tell you something.