I am currently near the beginning of the game (Mars Archives), and I'm at the point in the area where I ride a tram. Soon after, a fight ensues. To reposition myself to a better spot during the fight, I've used Tactical Cloak to become invisible and move to the other side of the room. However, a few times when I have done this, enemies have shot at me.
I realize that there's some fade time involved where I'm still partially visible by enemies, but even after I'm fully cloaked, I still occasionally get shot directly in the head and die.
My Shepard is level 33, has level 5 Tactical Cloak, and I'm playing on Hardcore difficulty.
Is this a result of me playing on a harder difficulty, or can certain enemies detect invisibility? If so, is there some way for me to tell which enemies can and cannot see me?