Crouching -Can make hostile enemies lose sight of you and search for new target.
Vanish -Forces your attacker to focus their attacks on another when entering combat in sneak mode.

What if there is no other target to focus on?

I play alone without companions etcetera so how will this work? Will They just search around randomly or will I have to be able to conjure a distraction to make this perk work? What do you think?

Difficult one. Maybe it just doesn't work when you are alone.
Plot spoiler, even though most people are aware already :

I believe that they will take a searching stance since there is no one to concentrate on thus enabling you to make a run for it!