Two nice articles speaking about player guidance, one is explaining how to work by opposition, declutter instead of adding more, one is explaining a technique about how to emphasize key elements, with lighting, but it could be props/textures/overlays etc.
Source is great for level designers who are starting out, because of its rendering limitations, it's important to alocate the limited amout of elements you have to the right area of your map. In those new engines, it's easy to lose focus and overcomplexify your design, which is going to bring troubles when the players aren't doing what they're meant to.
It's important to understand that adding more details in a map doesn't necessarily means that it's adding any significant value, when you're playing an entertaining game, how many times do you take the time to look at the stair design in a building ? The key is to put the work on the most important part of your map, and simplfiy the rest as much as you can. If the stair is the most important element, then overdetail it, but in your case it is not. The emphasize should be put on where the ennemies are going to come from.
Now it depends of the game, but if you're working on a Valve game, those are the rule for efficient LD.
I'm not going to say what you've got to do, you're the level designer, it's your job not mine, i'm only pointing out a flaw in your design, and that's the only feedback you need as a LD, don't listen to the feedback, listen to the complains instead, i'd rather listen to someone telling me it's shit, than hearing someone who never opened hammer explaining me how to make my map. (Listen to me though).