The best solution to that is to have two types of token. You get your usual token for completing the run but if you want that awesome "speed run" loot you need your high tier token or whatever you want to call it, which can only be obtained upon completion of a speed run. These tokens can purchase the loot that is obtained from going the extra mile in content. I know we won't have speed runs in ARR but there will most likely be similar challenges that reward players who do more than just waddle through.