Attack stance adds 1 to Attack, Archery and Magic and trains the weapon's skill. Defence stance adds 1 to Defence, Evasion and Warding and trains those instead.
Damage per second counts one attack every Attack Speed seconds. Time to kill runs from the first attack to the last one.
Not included: the time to walk to a creature or wait for it to come back, item abilities such as Barrage, and creature buffs during a fight.
How it's worked out
Skill damage 2 and skill accuracy 2 from Attack (current levels: potions and stance included).