I built Ilmango's Endermen XP farm and its really fast. But one problem with the design is that the Endermen aren't one hit kills, unlike other (slower and larger) designs, since it doesn't drop the Endermen from a high place (since the lower the spawning platform is the more Endermen) to get them to half a heart. They require around 2 - 3 hits with a Sharpness V diamond sword (other designs only need a punch).
So, how can I reduce the health of them without using fall damage. They seem to teleport out of suffocation traps (which are anyways too slow) so is there a method other than fall damage to get them to half a heart?