Idea The XP system

If there was it would be too op and anyways if you're lucky enough you can get a quadruple mob spawner. I think in your case you just found a single spawner. Usually a double/triple one can get 30 xp in about 10 minutes Afk at the right spot so that mobs can spawn faster and in more numbers

 

I have like a 8 spawner. Needs two people to make them all spawn, but it works. 7 Spiders and one skelly.

 

Lol wtf, I saw a video by a mindcrack player who had a 12spider, they were all up and under eachother, it takes just 1 man to afk tho.

It was in a mineshaft.

 

That's a ridiculous cost-to-reward ratio, given just about anybody can get their hands on a diamond block with relative ease.

We really don't need xp boosters, especially considering the importance of having high-level enchantments. By reducing the value of enchantments, we drastically decrease players' incentive to be protective of items such as p4 armour sets. Since preserving enchanted items is a key factor in deciding whether to engage in a fight, this little feature would effect a somewhat larger-scale change on pvp in general, which we really don't want.

 

In 1.7 I can see the possible values of having something like this added, although as Phanta said - your cost-to-reward ratio is terrible. I can take someone less than 20 minutes mining to get an emerald block and would make getting XP way too easy and unbalanced.

1.8 made enchanting a tonne easier. Since you don't go back to 0 XP after enchanting a level 30 item, you only lose 3 XP levels. XP is supposed to be very valuble since it allows players to get good enchants to fight with.

Very bad idea IMO -1

 

Perhaps try other designs with your mob farm, go cave lighting, or just keep looking for more spawners to increase your efficiency.