Only for the sake of simplicity really, in truth you can do them either way round or even at the same time once you get used to what each adjustment is likely to affect. Generally ARB's have more of an effect on the grip limits of the car than the dampers which are responsible for how that grip is applied, it is more important to know where the physical limitations of your car are so you can work more effectively within them. When I tune a car I don't really follow a specific order for adjustments, I can work out fairly quickly on a test drive what needs tackling first and will start from there but this comes with experience. Its a complicated mental process to explain because there are a lot of considerations that go into every decision, lots of little bits of physics theory that affect the bigger picture (eg. tyre theory or weight transfer)and its hard to know what to explain and what you already know. The damper tuning process should hopefully help stick some of the pieces together because the way they operate is brilliantly simplified, it might sound a little confusing at first but once you get your head around the concept then all the rest of the pieces fall into place.