A torsos HP is a single stat. At the beggining of the game you only gain +5hp from your torso. However if you use a weapon with +1 damage the 5 or more times then you are canceling out the torso HP or even adding more damage than the torso would give. Quite often you'll have one prefered weapon that does the most damage. This one is the one you should level up first and try to get in range of your opponent most, and if you get 5+ attacks from this weapon with only level 1, the +5 hp is cancellled out