I did run into that issue with the events hitting all grenades (primarily seen by them all exploding then one grenade’s countdown was over even though the second one was fired later).
One thing I did though was the grenade only immediately exploding with an enemy when it was still in flight. As soon as it hit ground (well, and being reflected by walls too), it wouldn’t react on direct enemy contact anymore, only explode on its countdown.
The advantage of it is that one can fling it near the ground at a group of enemies more easily without it exploding too soon… 