Interesting concept. I couldn't really see the enemies for the first 2 times I died, I was just wondering how to fight back and know where to shoot.  

I suggest keeping the health reduction speed slow for the first 15 seconds so that people can orient themselves and figure out that the health slider is not a timer, the blue thing is cursor+lifesaver+torch. (which was the interesting part.) 

Start with dimmer light.  Low damage, low pressure environ. Let the player realise - "Oh the HP slider is falling".  And then introduce 2-3 free souls. Honestly, if I wasn't annoyed by the "timer", I would've been very pleasantly surprised by the way the cursor brightens up.

And after introducing the player to the core mechanics for survival, get creative with whatever ideas you manage to implement ^_^