I hadn’t experienced this prior to the DLC:
At times I lose the ability to “Split-Up” and “Re-Group”. The on-screen prompt is gone and the assigned key does nothing. Also, the ability to Exit Combat will also vanish. Along with this, several times I am unable to Recall or Hide. Again, the on-screen icon is missing and pressing the assigned mouse-button does nothing.
Sometimes saving and reloading will bring them back (but no always).