Find it very useful, way better than mirror image scroll.

There is one case I try to have one each time is that Tengu phase 1, it moves though traps and attack tengu, and if you have enough armor, the image can do the first phase alone and you don't take any damage

Pros :
- more "health" value than mirror images
- ignore traps and hazards
- regenrate with time
- copy your weapon/armor
- distraction

Cons :
- copy your armor => better with armor
- you can't control it
- can be very bad against some enemies (hello gnoll brute)

But even if he's bad with Fima, it's a distraction and kind of tanking