The only things that give stat bonuses are the things that actually tell you. So the facemasks/helmets don't do anything aside from looks.
And yeah, the duels in Lethal will always be like that. Even end game when I had maxed out armor and for the most part had charms suited for survival and a good amount of max health buffs I would die to some attacks in duels in 1 hit, and other attacks would be 2-3 shot kills. Often they attack in combinations so even though something might be a 2 shot kill on you, if you don't react to the first hit you usually get bopped by the second one too.
I would recommend managing your resolve so you have a few at all times just in case you are about to have a duel. Sometimes it's more obvious than other times, but basically if you go into a tough Duel with no or very little resolve it makes it 100x harder as you can't heal yourself or revive yourself.