Rework damage models

After playing a few rounds me and my friends had a couple of gripes on some of the damage models for certain things.

The Human Shotgun
Way to weak and its inconsistent on how many shots it takes to kill at close range. Sometimes it 3 sometimes its 4 please fix this or this weapon will become unused.

Grenades in General
Sometimes they full kill if your standing on them other times the enemy will full tank the grenade.

Melee Glitch
There is a exploit allowing users to multi punch at the same time and can insta kill we had one guy flatten our entire squad by just meleeing

Commando Damage
Commando seems to have an extremely high DPS rate almost making it dominate in long and close range possibly just slowing the fire rate will resolve this issue.