Speaking as a PVE player, I’ve come to love Flashbangs.
In higher difficulty Escape they can be so useful in tight situations. If you flash-stun enemies you can do the quick meatshield executions and it’s basically a free kill or two. Plus if you’re doing this to Elite Grenadiers you get a free Flashbang back for every one you meatshield.
Plus they are useful for melee-classes against Scions allowing you several free hits to bleed them without them taking any swings at you.
Also from an Escape perspective, I love setting flash-shock grenade combo traps - basically planting a Flashbang and a Shock on top of each other. The Flash stuns enemies in place while the Shock does the damage. It’s great for Juvies because they normally move fast enough on high difficulties to avoid being killed by the Shock alone so the Flash is great for locking them in place.
