That is not correct. You can perfectly change the damage every weapon does, even to each region (head, upper body, legs, etc)
lowering the HP will make all weapons more powerful, so that's not the same idea.
Take a look at my Terminator invasion MOD. I altered the damage for the interventions only, so that Terminators could be killed with 1 headshot or with two upper body shots.
I had to do this, because terminators have insane HP, so an intervention with the default damage would be useless (took about 6 or 7 hits..)
If you want to learn how to do this, download my mod and look at
_damage.gsc
and
interventiondamage.gsc
Good luck!