That's not purely the fault of boss/progression design, though. Guild Wars 2 has one system and WoW has one system, and they are both likely to have their flaws. The solution to a shortage of content at end game is indeed a design issue, but more to do with designing a world which is fun to be in to begin with, with lots of useful tasks to perform. Scaling bosses, I dare say, is a lazy solution. Fortunately, GW2 does seem to have plenty of other things to keep a player busy apart from bosses, so I don't mind really.