From my experience playing the game Path of Exile, adding more Attack Speed and on the other hand adding Increased Damage assist an RPG character more or less depending on how much of each you already have, and how much you have relative to each other.For example if you do 20 damage per attack and attack once per time unit, and you have a choice of increase attack speed by 25% or adding 5 damage, you have increased your damage per time unit by 25% to 25 dptu. But if you add another additional 25% speed to get 1.5 attacks per unit, then you are only adding 5 dptu (to 30) and would be better off adding 5 flat damage because that would take you to 31.25 dptu, 6.125 instead of 5.
All of which doesn't mean much as I don't know exactly how much attack speed is added per point of skill in MM6/7/8.
in my new solo mm7 game I am going on faith that I will be able to get a super fast attack speed with GM Bow and a Bow of Darkness that I picked up from the Emerald Island dragon.