Gaerzi: The highest difficulty is a bit bugged in ZDoom because it uses the same adjustments as Doom's highest difficulty, which includes increased aggressiveness for enemies. In vanilla (or Chocolate Strife, or SVE) you'll find it a lot easier:
You can see on these videos how the Bloodbath start is much easier normally, with acolytes that don't shoot you immediately and without stopping:
http://youtu.be/O8UKGuLStqA http://youtu.be/jDRFPDiHR_Y Basically, the AI for enemies has to make them choose between moving and attacking, they can't do both at once. Normally they choose moving quite often; but in Doom in Nightmare, they'll choose attacking nearly always if they have line of sight, so they tend to stay in place and shoot constantly as long as they see you. In Strife the probabilities for choosing move or attack aren't changed by the skill setting, so the acolyte will move around you instead of shooting you, which makes this much easier.
As much as I love ZDoom, dont get me wrong, I love the port, its how I play Doom I & II/Heretic/Hexen most of the time
(I briefly gave Doom retro a try, and while I think Brad Harding is a cool guy I went back to ZDoom due to smooth doom).
I have to say I perfer VE for playing Strife, If you guys could patch in some form of SVE.wad support ( I doubt it due to legal and technical/programming reasons) It would be awesome.
But yeah dont take this as a "I hate zdoom post"