I previously reported that Step Back wasn't working when I got to the level where I unlocked it. I had my first battle tonight after leveling up and getting Fast Aim I find it too does not work. I'm on version 1.3.53 playing the Lost Valley campaign. I had just finished the CotM campaign a week before Lost Valley released and it was working then.
These skills still do not work after 1.3.55, even though the patch notes say it fixed Fast Aim. With 1.3.55, Fast Aim shows up now as a bonus action, but it does nothing when used.
I managed to complete the Lost Valley DLC a few months ago despite the bugs, and I haven't played it since. I have seen several updates since then, so I decided to fire it up today. I load a save near the end, get into a fight, and... THESE SKILLS ARE STILL BROKEN! The game is showing version 1.3.82b.
Step Back appears to be working for me. Have you tried Version 1.3.91?
I see there is a new DLC and a new patch 1.4.24. I just loaded a save where I could get into a quick fight and these skills are still broken.