OK, grabbed a DX2.0 and went thru the menus. Let's verify that you have your throws maxed out:

Press the Scroll Button 4-times until you get to the EPA screen

If it says TH on the screen, press the Channel button once to select the ST mode.

Turn the wheel to the right. This will allow you to adjust your throw to the right. When this is complete, turn the wheel to the left and adjust your throw to the left.

From here, Grip Button B will allow you to adjust your overall steering throw.

If this doesn't work, check to make sure your steering links aren't binding up, that your servo is working properly, and you may want to bind your receiver to a different transmitter to just double check if it is a radio issue.