I did some testing with hidden mashine and here are my conclusions. I tested the following situations:
The enemy is idle, has not noticed me
The enemy is attacking me or is repositioning
The enemy is attacking my pet or is repositioning
Fade Away: The enemy is attacking the ground, where I was standing when Fade Away started, or is repositioning to attack the ground
Hidden Mashine works in the situations 1 and 3, but not situation 4, which is clearly a bug.
So, if you want to trigger Hidden Mashine, try to create the situations 1 or 3. However, sometimes it is difficult to determine, why the enemy is repositioning. It can be situation 2 to 4.
Without Fade Away, it is difficult to create these situations and trigger Hidden Mashine. So it is probably worthless in Rakk builds.
Seems like best is Gamma Burst and have your pet grab all the agro. For Rakk builds you still do get Galactic Shadow which you are less likely to be attacked.
Yes, with the Red Fang class mod Hidden Mashine will trigger reliably.
Galactic Shadow hasn’t convinced me yet
I don’t notice any difference except the critical hit damage.