Quote from Konar6

Quote from Baker
[...] It has sort of become an issue while playing singleplayer. I've noticed that all enemy attacks do minimal damage on any difficulty that I play on.
I usually play on Ultra-Violence, and I noticed that when I'm hit by anything, be it Imp fireballs, gunshots, or melee attacks, I either take no damage at all, or I only take a small amount of damage (1-3 hit points). Keep in mind that I have no armour on while this is happening. The only constant damage I can regularly receive is floor damage.

Isn't your SV_Coop_DamageFactor altered?