Wondering why riot didn't implemented a predator steath mechanic yet
I would just make a lot more sence:
- When not moving you are compleetly stealth
- When you are moving the transparent background get's a delay (so you notice something is out their)
- When you remain in the vision of a enemy champion longer than 3 seconds. You come visible in stealth form for the enemy champion (only for that champion tho)
- While in combat the stealth rapidly declay
Just think about this mechanics for 

