Well, I mean, if I end up in melee, I get murdered. If I have to deal with two enemies at once, I get murdered. When I first come to a new town, I spend a while just killing things near the stairs/gate, because if I stay in the dungeon for more than a few seconds, I get murdered.
I have pretty great leather armor, so I can take two normal hits from a normal overlevelled monster.
It sounds to me like the problem is mail and plate aren't that much better.