Did you use trackball friction at all? I've found setting mouse to trackball mode and setting friction to low to be the best solution for turning around.
You could also set your default sensitivity really high and use mouse dampening with one of the triggers to make aiming more fine-tuned, OR set up a button to act as a mode-shift for the touch pad to make a secondary, high sensitivity (sort of like a reverse dampening). The customization is almost limitless and a large part of what makes the Steam controller so great.
I haven't tried this feature yet myself but based on what I've read about it, Terraria might be a prime candidate for the 'mouse-region' setting on the right trackpad (or at least as a mode shift). It's a relatively new feature so it hasn't been incorporated into many official or community bindings yet.
This is exactly what I mean. There is so much to tinker with this controller, even on a game to game basis. I'll Def be trying your suggestions. I'd love to get the Terraria controls down anand use em to replay through Starbound. Again, thanks for you're advice.
Also I've been using the controller as my only input on my surface pro 3 hooked up to my tv and it feels great.