Minecraft – Why can I not join a game on Minecraft xbox360

Typically mobs don't just run off ledges hanging in the air. They will however jump/be pushed into water at their level.

Judging by your pictures, there should also be more mobs - I would reckon that there are more caves and ravines to light up.

But, the important part is this: this design typically requires water streams at each level that funnels the mobs to the center. The mobs get pushed or jump into the water at their level and are funneled and dropped into the center. I have a similar setup, and this is what I have done, and it works adequately.

Please keep in mind the spawning rules as well: http://minecraft.gamepedia.com/Spawn. There are certain distances that must be observed or else mobs will despawn or not spawn at all.

you need to be connected to the tv/monitor via HDMI cable, some earlier model xb360 do not have this type of connection. However, later one do have both a vga and HDMI, connections