I have an enderman xp farm in the end which now causes insane lag. It worked without any issues prior to 1.13. More specifically, it lags only when endermen are falling. After the initial drop when they are all contained, fps return to normal. I'm confused as to why that could be, considering it handles large numbers of mobs with no problems otherwise.

EDIT: I've discovered the real issue. While it is related to the mobs falling, it is actually the particle effect from the ground. I will change the title accordingly. I still feel this may be an optimization issue. I say that because it worked without issue in 1.12.2. I will leave this up to see if anyone else has the issue to confirm. 

EDIT 2: Obviously the resolution is to reduce particles, as that many particles can't be handled without lag. Yet it worked prior to 1.13, so I'm still concerned about optimizations. 

To reproduce: 

 I've found it rather difficult to do so without an enderman farm. It seems that the mobs have to hit the ground in different places to create enough particles to cause the lag. I'm unsure if this means that only a certain number of particles can occupy one block, as I've attempted to use a command block to repeatedly spawn mobs to fall but the particles created aren't near the same amount.