It's a different perspective on RPG progression, if you consider it for a while. What popular RPG employs a downscaling system like GW2?
ArenaNet is asking you to look at character progression "showcase" in a different way, instead of the traditional way (which is to go back to old areas and steamroll everything in one-shot and large numbers). Consider for a moment that progression in GW2 isn't based on stats or the amount of grind done, but through development of your skills and strategies. This is reflected by the lvl 1-30 experience: it is less about gaining stats, and more about unlocking more skill slots and skills in general. It is less about boosting numbers in your trait line, but more about the minor traits and the choices of major traits. It is less about standing around and dealing one-shot blows, but more about reacting to ever-changing situations and shifting your builds/roles constantly.
All this is added alongside the other benefits of downscaling, such as old content remaining challenging (which means less rehashing of content later on), less tension between players on each side of the power range, etc.
Level downscaling as a RPG concept is relatively new and revolutionary, but it requires thinking outside of the traditional mindset of progression to be fully appreciated. It's both refreshing, yet threatening, as it virtually removes what makes an RPG: stat progression. And puts RPG progression on the same page as, say, an old-school FPS progression.
What I'm trying to say is, don't treat GW2 character progression like any normal MMORPG character progression, or else your understanding of the system will be stunted. It's more about the progression of your skills as a player and your ability to create/change builds, not your stats.