Still working through Rank 9, I found out the following. The XP bar is about 300 pixels wide. To fill one pixel, you have to kill 18 monsters that give 217 xp a piece. If you can kill three a minute solo, Rank 9-10 takes 30 hours of straight grinding to hit the approximately 1,171,800 total XP. Hence a solid weeks worth of full time grinding. PUKE!!!!