A very nasty cheat to detect enemies that have turned invisble is to see where your movement path goes around an obstacle where there is none to be seen. Next, you can throw something, like a water bottle, at that spot and reveal your invisible enemy. It is cheating that can be hard to avoid if you are just scouting around for movement options.
Also, enemies that turn invisible tend to stay where they are. It would be better for them to move somewhere else after turning invisble. Else they are too easy to reveal, again by just throwing a water bottle at the spot where they disappeared.
To solve the path reveals, I'd like to suggest for the pathing to ignore invisble characters. If your move happens to end at the exact spot where the enemy is hiding, let them take a small step sideways, and/or let them roll a die to avoid detection.
