Hi, just played this (as a vampire on normal difficulty) and would like to offer some constructive criticism. The overall level design is not bad, but unfortunately the gameplay is hindered by many small oversights and some bad mechanics. For one, the mechanic of slowing the player down when they reach >20 health is just flat out terrible. One of the joys of FPS games is managing to scrape by despite the odds being against you. This pretty much guarantees your destruction if it happens during any high-intensity combat. Second, the vampire's weapons are not very satisfying. His 3rd weapon can't even consistently one-shot an ettin, which is ridiculous. I didn't realize alt-fires were implemented until I reread your post after finishing the game, so maybe the alt-fires are better. But the primary fires are just too weak and unsatisfying. Third, the 3D models are a mixed bag. Some (like the catapults, trees, & barrels) fit in well with the world of Hexen. Others (like the corpses and boulders) clash terribly with Hexen's artstyle. Finally, there are a lot of little errors and odd design choices that hamper combat. For example, many places that it feels like the player should be able to go are flagged impassible. Here are some screenshots of just some of these issues I noticed:
https://i.imgur.com/tkDnSwY.png
Why put this reachable ledge here if you're just going to cockblock them at the end with an impassible flag? Also that little triangle is a visual bug. Something similar happened on the farm, where there's a pile of crates you're obviously meant to platform on, yet at the end you're met with absolutely nothing but a nonsensical impassible line.
https://i.imgur.com/qtGfkGA.png
These guys can infight with eachother. Not sure if intended.
https://i.imgur.com/wPBtr3F.png
Pressing use in this open doorway still results in the locked door message.
https://i.imgur.com/Rw6IKzf.png
It feels like you should be able to open this door since that's how the area was working up until then (pressing switches to open doors). Why put the door there if it has no purpose?