for dungeon defenders did you turn on relative touch for the joysticks? You have to double tap the button and choose button properties. Otherwise all it does is emulate a tap on one of the 4 sides of the joystick "ring". With relative touch on you get a lot finer control. Give me a bit and I may be able to throw together a few touch profiles for Dungeon Defenders and Shadowgun. I haven't reinstalled them since setting up my dual-boot so I need to download their sdcard data.
EDIT: Scratch that, no relative touch on Dungeon Defenders. It works better without it in this instance. I'm working on the mappings right now.
EDIT 2: Heres the Dungeon Defenders profile. I tried to map as much as I could, but it really is a game designed with the touchscreen in mind, so full functionality is impossible. What I do have will get you by 90% of the time with the controller only. I also put together a profile for Lego Batman on OnLive. The control setup will work for other games too, just not 100%. As usual make sure to rename the file to .map and put it in /sdcard/data/com.dancingpixelstudios.sixaxiscontroller/ or go to Edit Touch Profiles-->Open Menu-->Load Profile-->Import then choose your file from its downloaded location.
Dungeon Defenders Controls
Left Analog: Movement
Select: Open/Close Map
Start: Pause (need to hit Resume to unpause)
PS Home: Activate Crystal
Right Analog: Free Look/Choose Defense Location
Square: Shield/Cancel Defense Placement
Circle: Attack/Place Defense
Triangle: Place Waypoint
L1: Defense Menu
R1: Hero Menu
Directional Pad Up: Defense/Hero List 1
Directional Pad Right: Defense/Hero List 2
Directional Pad Down: Defense/Hero List 3
Directional Pad Left: Defense/Hero List 4
R2: Defense/Hero List 5