I try to set mine up so the 3PH frame is level. Doing that makes the kingpin vertical. IF this isnt how you got it set-up, if you angle the blade, one side will be lower than the other. But with the frame level and kingpin vertical, you can angle it however you want and not have to re-adjust anything.
That said, Longer TL bites more, shorter bites less. But it sounds like a combination of a light blade and rock-hard ground. In that case, there isnt much you can do until you break up the soil somehow. Tiller, middle buster, box-blade with rippers, plow, disc, etc. My 700lb blade dont even bite well if it is really hard-packed like cement.