.
Basically, I fixed the problem with hitting an enemy directly with the main grenade. You couldn't ever really make good use of cluster grenades because monsters (and players) are too hard to lead into the trap, and if you accidentally hit them with it directly it explodes for much less damage.
My solution:
If the grenade doesn't hit anything but walls, it splits on a timer as normal.
If you hit a target, the cluster grenade still splits, but the mini-nades don't immediately explode on the target. They fall to the ground and then explode. The resulting effect is perfect, in that it carpets the area with explosions and slaughters everything in the area.
Now THAT'S a cluster grenade.

Funny that this is what finally got me to make another mod. lol!