Earlier today I made a Dark room mob spawner for the drops, now once in a while I get a mob to fall, using the guide I followe I made the exact same room in my SSP and it rained mobs, so it's not as if my design is wrong. might be bukkit related, I hope it's fixable anyway >.<

If you want to see for yourself
x 2788.5
y 200
z -85.5

Old survival world