the issue with a guild wars 2 model is that you can never really feel like the hero as no matter how low of zone you go to you are not more powerful. There is something visceral about mowing down opponents who only mere levels ago would strike you down if you were not careful.

wow mediates the issue of content going stale by allowing people to mow through, especially older raids to get accomplishments and gear; mostly for transmog of current gear or mounts and pet. This to me is a better solution. The GW2 solution leads to a more annoying world, where everything has to be taken into account and there is no breezing past low level content on your way to more excitement