Blaze farm

with all that EXP floating around it may cause lag,even if jab has fixed it,in large amounts it will still lag,like having a few hundred entities at once causes regional lag,exp farms cause epic lag as they put of 1000's of entities per hour

It only outputs experience when a human kills an entity,

this video is human powered in the nether, most people are in the real world

a player must be close enough to the spawner for it to spawn mobs