Level kit gives you a nose up stance with any load in the back. Generally, any changes to the suspension form stock come at the expense of something else. It does look like weak springs too, but dumping the level kit should help.
This.
There's a reason that trucks have a raked stance. When you set them up to be level, unloaded, you're going to get a bit of squat with a load. Part of this squat is the result of people expecting a car-like ride in a truck, resulting in springs that are a bit soft for the for the first couple inches of flex.
