After several hours of investigation it looks like there is no problem.
The player Benjeh hit Rank 13 for the first time on June 24th. That means the previous week the player had at MOST 54999 rank points (99.9% progress in Rank 12). By attaining standing #1 the player was awarded 13,000 rank points and suffered a decay of (at most) 10999 rank points. The highest rank it was possible for the player to attain this week was 40% progress through rank 13 or 57000 rank points. Rank 14 requires 60000 rank points.
The players in standing #2-4 already had significant progress through Rank 13 and due to having only slightly less honor (contribution points) than the player in standing 1, they receive only slighly less rank points.
For a detail explanation of how the honor system works in vanilla WoW please see http://wowwiki.wikia.com/Honor_system_(pre-2.0_formulas)
