This is my run of heretic.
Episodes are done seperately, each episode is single segment.

Makes it down to a 22.20 overall time.
E1 : 7.04
E2 : 6.51
E3 : 8.25

Using ZDoom engine.
Using items with keyboard bindings, which is faster.
No jumps or crouch or whatever.

Better times have been done since, you can check    / @cyanveo1850  
for some nice runs on a more vanilla version

  / 45247332   this is Episode 3 WR for ZDoom
  / 45247384   this is Episode 1 WR i believe on ZDoom as well.