(UPDATE: 11.05B tablet edition has a max size slider above size, setting this will limit the range of the sizes and make the pen less sensitive, though the advice below is still valid and useful so I am leaving it)
For the moment, please go in to your tablet settings on your computer and change your pen setting to be 'harder'.
This should help some.
Also be sure to range the tablet properly when you start the app,
You need to press down really hard so we understand what the max pressure should be for your tablet.
If you have an eraser, set it to be really soft, and press down with it to range the tablet instead, it tends to work better.