Grenades: Oh, the disappointment

[Grim Lightning Gate]

Okay this is what I know of them so far, no a lot I must add...
One, they stick whenever they want, but MUCH more so when others are using them

Two, if you don't HIT something with them, they will NOT injure the enemy even if they show the subtraction in red.
Once you HIT someone, it will dole the damage out to all the surrounding enemies in the area

-GLG/CBF (bark bark)

[Zhalin]

Yep.
In other words, these things need a lot of help.