This may require you to tweak the layout a bit but you should add some random gates that block the survivors and force them to go a different path.
The gates could be textured the exact same as the walls of the maze or something else. Make them as func_doors and make their spawn position to start as closed so that they start off blocking everything. By doing this, the func_doors will have the correct lighting on them rather than being pitch black.
THEN, put a logic_auto somewhere on your map and make it fire the output ( OnMapSpawn -> door_* -> Open ). This will open all of the func_doors on your map if their prefix is "door_". Now all your doors are open and ready for you to start randomly picking.
THEN, make a logic_case for a group of 2 or 4 doors as it will pick only ONE of them. In the logic_case, set the outputs of case01, case02, case03, etc. to open a single door.
For example, in the logic_case outputs, ( OnCase02 -> door_02 -> Open ). Now go back to the logic_auto you made and for its outputs, make it fire to each of the logic cases. So for the outputs of the logic_auto, ( OnMapSpawn -> logicauto_01 -> PickRandom ) and then for the rest of the logic_cases you made.
Sorry if this appears confusing but it could really help take out the linear aspect of the map. Contact me on Skype if you want help with this.
Also, make a room that a player gets stuck in with Slenderman inside and
this music playing.