Auto-Attack can be define as: The ability to perform an action on a target based on a predetermined delay with no interaction from the player.

Does the presence of an "auto-action" option affect the actual pace of combat?
No, that would be based on the predetermined delay of said action.
Does an auto-action allow you as a player to do MORE in combat or to do LESS in combat?
Neither, it is simply an auto action.

The question that needs to be answered is do we want a fast pace battles like WoW (I hate using it too but it is the current MMO template) or slow paced like FFXI?