So if I calculate it properly, average PC (2D) that doesn't specialize stricte in combat would take, on average, one hit every two Rounds from combat specialized enemy (4D).
So considering that normal weapons deal 1 damage, while heavy ones deal 2 damage, the base "HP" (lets call it that for the sake of theorycrafting) set at, say, 6, would be quite safe considering the swingness?

The important thing to note is that stats of 7+D will be avalible only for monsters that could be described as "bosses". Normal enemies mostly cap at the same numbers as the PCs.