I have a hard difficulty survival server but the mobs seem slow. Like I can run up to a skeleton or creeper and stand in the same block as them for 3-4 seconds before they react. Doesn't seem to affect zombies. I haven't altered any settings of Spigot or Bukkit's yml. I don't have any lag. My average TPS is 19.86 and my server load has yet to go over 25%. My host advertises 1 GBps speeds.