Go and spend a little time in Edge of the Mists. (hit B to join). Each WvW rank will get you 6 to 9 hero points (and a book worth full level of xp). You do not get these until you are 5th level in WvW.
Takes little time and the rewards for the first 5 wvw levels is wvw xp bonuses, so goes really fast.
So about level 10-12 WvW you have 30+ extra hero points so you can unlock Reaper faster. Save the xp books for an alt if you want to just level slower.