Back when the equivalent to the 1.5 update came out, I could tell a slight decrease in the efficiency of my endermen farm.
With the most recent update though, it's unbelievably slow. It's the traditional Docm77 farm, it's made out of 18 lvls (x2 of course),15 long spawning pads, and it doesn't go above 128 on the "Y" coordinate since I heard it wasn't going to help it.
I mostly use it for repairing atm, and the anvil costs got reduced a lot, so it's not that huge of a deal.
Has anyone experienced this? I'm quite salty about it but I can live with it if it's a permanent change in the mob spawning.
As close to the edge as possible and as low down as possible. He spent time drop down a water stream to build downwards as much as possible, to I think y2 he managed. Apparently having the spawning platform as low as possible helps, so they fall to y2. The island was all lit up already so that helped.
Thats not the reason at all for reaching the lowest Y value at all, its so that one can have as many platforms and spawn floors as possible. If one starts the farm at say Y:60, then you have 60 blocks below you that are not being used for you farm. There is no reason other then to attain as many spawn floors for your farm.
Before you construct 'an endermite' farm, I would suggest testing if endermen are aggressive towards endermites. Way back in snapshots of 1.8 they were, but endermen were later changed not to be naturally aggressive against them. If endermen are not aggressive towards them then your building a dead farm, in other words one that will not work. I'm doubtful that this is the case. If it is I'm kinda thinking that 4J will fix this like mojang did on the PC. This only worked in a snapshot or 2 before it was changed. Even if they are aggressive towards the endermites, i would personally be weary of building this type of farm, especially if you don't want to take it down or have a dead farm.
Like I said I doubt this will last. Endermen are supposed to be passive towards endermites. I expect this is an over site on 4J's behalf. I think i'll pass on this type of farm, even though its not complex to build, it will be a pain to tear apart once its been patched.
I'm apparently wrong with my knowledge of endermites. I just checked the wiki and it is default behavior for endermen to attack them provided they are not tracking a player.
However that said the farm is not more efficient then other endermen farms per say, just much easier to build, and costs way less in resources. In fact i would say it is slightly less effective in that it uses up 1 hostile mob count for the endermite, however not something one would notice unless spending hours at the farm.
Personally i think that if one already has a endermen farm with a lot of spawn floors, they shouldn't take it down to put up this farm, however anyone starting a new endermen farm should highly consider using an endermite design.