It's not 100% randomized, at least with enemies. There's set enemies that either will or will not be there, with some far more likey than others. It seems random at first but as I played the same segment so many times I did figure out it was random if they're there or not but their placement and purpose for being there was not random.
I haven't played the whole game, but in the demo it was not a problem. I think it seems more like a problem if you think about it rather than in action, at least from the demo. As there's multiple ways to tackle a situation, it becomes sort of... Natural to try and work with what you've got.
More enemies isn't always a bad thing. If certain enemies spawned carrying an axe, for example, I could then pick up that axe and use it to melee an enemy efficiently (axe is a one hit kill on a Haunted, but it also breaks after you use it), and the enemies can distract each other I think (I noticed some doing motions to each other, or bumping into each other and groaning), so their preoccupation can make it actually easier to sneak past them.
The game sort of sent an inner challenge freak in myself, I think because the game is fairly challenging even on normal and and has a lot of attention to detail, but it sort of... Promotes a feeling of judging survival rates against uncertain odds, but giving you enough to work with and you gain enough knowledge of the game and it's world that you ask yourself if something is worth a gamble, or if this scenario would be best to use limited ammo or to try and sneak/run past, or you get this idea to wait for these three enemies to be next to each other and then use an explosive bolt and let the magic happen.
If I think about it, it seems problematic, but while playing I never found it a problem, at least. The enemies seem to have well thought-out points that, whether they're there or not, provide new possible challenges in an area.