Umm...you can do AOE tests with the dummies too. The point is to be doing your comparisons in a controlled environment...or at least with as much control as you can. The dummies make it really easy too since you don't need third party parsers. They all start at 100%, and you compare how many you take down and then how low the last cycle is when the time is up.
Pre-58 it can be a tight comparison...and even after completig things to 60 it almost requires you to be slamming everything you've got in the kit in the right rotation to keep a double digit lead percentage wise. Slip up, and you may find yourself in the 6% range...a little more out of synch and you cross into a difference more akin to making better choices in gear or food.
Alternatively, SE could have given us Valor Minuet as a flat boost to attack for self and members in range and given us the extra skills and basically not forced a different (and less forgiving) play style after nearly two years and 50+ levels of gameplay.