excessive Zombie pig man spawning

My friend and I recently uploaded our world to Realms.  So we already had a neather base set with a highway to the endportal.  The first time I try to use the neather when the world was on realms there was about 50+ angry zombie pigman sitting outside the portal in the nether.  we ended up killing them because the server was kinda laggy so their pathfinding was a little slow.   Now every time I go to the neather there are angry zombie pigman there. It appears the longer the wait in between going to the neather the more zombie pigman there are.  it got so bad at one point that the server was excessively lagging when I tried to enter the neather.  So bad that I couldn't open up a menu or walk.  I fixed the issue by leaving the world and changing the world to peacefully entering the realm and then changing it back to hard.  It has gotten worse now anytime you try to enter the neather you are insta killed by a zombie pigman.  I tried covering the entire area inside and outside the neather base with slabs but to no avail, it is just instant death.