They work well but sometimes they don't even give a hit marker even when it is right next to the guy.
Its fine. Best offensive equipment in the game that replenishes with Scav. Any more blast radius and it would be considered OP.
I'm not saying increase the blast radius. It just doesn't work at all sometimes when it is right next to the guy or at his feet.
All explosives are like that. If anything should be done to the C4 though it's limiting the distance it can be thrown