Combustion sucks now. It is delayed and they have to be within 3 feet of the guy who got killed then stand still and wait for the explosion, then it might kill them. Otherwise IF they even get hit by combustion explosion it does negligable damage, I have seen values ranging from 12-75. Hos has 3-4x bigger blast radius and less damage drop off at the edges of explosion. I dont know if you play gunslinger regularly but the aim assist you speak of is just not true. Not to mention that you are a glass cannon and have about 10 seconds to fire off 3 shots. Overpenatrate is fairly useless in pvp.