Kharn...
Edit: saw your update. But yeah, that is all incredibly out of date.
For example, that xp count you gave will get you near level 31, but not quite there yet. Not level 33. And heirlooms don't have increase requirements. And there is no extra weapon proficiency for retiring. Wake up, man.
As to the main point, the fun is the purpose of retirement. For throwing, heirlooming is incredibly useful in my opinion (an extra shot per slot is huge). Plus, a masterwork weapon is way cooler than a normal one.