I've observed, and experienced myself, an issue with the behavior of creepers when they attack the player. Sometimes, when a creeper drops from a height (for example, dropping from a ledge in a ravine) next to the player, the creeper will not sizzle before exploding. Thus, the player has no chance to get away, and will often die, as the damage will either instantly kill them, or bring their health down significantly. I have also experienced instances where these explosions will vertically launch the player around 4-7 blocks, usually causing additional damage.