Ok, I have played a lot of servers with custom content and I have noticed something, your mobs have "horrible" hp setups, its either A.) Too Much, or B.) Way too less, I saw a level 45 mob with 1200 hp... So, I made a chart for level 1 - 60 mobs, Named, Normal and Boss Mobs...
http://leetninjas.com/rich/HPChart.txt