I'm playing the Direwolf20 Modpack and I'm trying to make a enderman farm where I can stand under a two block tall platform and look at enderman but when I do this the enderman come to me and then teleport me out from under the two block tall platform.
Is there a mod that is causing this to happen.
Nope. That's the New Improved Endermen(tm) behavior in Vanilla.
Am I the only one that follows Vanilla development? (hypothetical question)
Mojang got wise to people cheesing Endermen in the exact method you describe, so they decided to screw with you. Now if they could just fix the backlog of known bugs and issues as they crank out version after version we'll be in good shape.