I think that those 2-week-patches are awesome if you think of how Anet iterates on content and listens to the community. They get our feedback constantly and take it into account for the upcoming patches.
This happened not only once so far. The latest example: RNG
In the upcoming patch Tickets aren't pure RNG anymore. Yes, there is still the golden ticket which gives you the item instantly, but now we also have fortune scraps. You'll collect those and once you've enough, you can buy the item even if you got no golden ticket. So there won't be guys who open 6000 chests and get 0 tickets anymore.
This wouldn't have been possible in a expansion. They would try something new and suddenly most people don't like it and it's quite difficult to go back - having opened pandoras box. Anet needs our feedback for improving the game and this 2-weekly updates are the best way to do it. They experiment with these things as we've seen and in the end we'll get what we want.