Reloading can be as complicated as you want it to be. I've often found that starting with good components and good reloading techniques often works wonders and makes things go much smoother. I've also found if a load or rifle is very hard to get to shoot, then it's not a great combo or there's issues with the rifle. A good load and good combo should be somewhat tolerant and not make you chase your tail. I've done seating depth first and I've done it after powder testing. Your mileage may vary, but I don't think either way is better or worse. I've found the same bullet at the same seating depth to shoot well at different powder charges and different powders all together. Maybe not optimally, but under 1/2 MOA. Things don't have to be over complicated. You may have to retune the load at times, but that's typical no matter how you go about load development. Just look into Alex Wheeler's "Keep it Simple" thread and the success they've had in long range benchrest.