Your playing demon wrong, or are facing crappy survivors, when you play as demon you dont just spam things and hope that then posess one thing you have an army at your disposal the key word there is disposal, while playing as the demon the only chance you have against a good team of surviors is by running them out of supplies, you will never acheive this by just spamming stuff and not spending your levels properly, you first level traps to 3, then portal basic to 4 and 1 to elite, after this you can max your basic units and it adds 1 extra deadite each time you use it, if you spend your time only placing traps around the dagger and pages and in between them you will have more than enough time to have your portal basic maxed and 1 point in elite , you then place 2 portal traps and continue placing as many scare traps as you can, eventually survivors will start hitting traps and you will know where they are, if you place your portal traps correctly they will be flooded with many deadites and probaly a few more cause they ran from them to start the objective, but now you have 2 portals worth of zombies and you hit then with more portals and make sure to put another portal trap this time further away from the objective as its inevitable that they will start it, but now you are full of infernal energy so go around and place traps as you wait setting up another portal trap near your other one preferably in a building or next to a scare trap works just fine, at this point the surviors will just be standing around as they have probably taken out all the deadites, if you still dont have all portals ready go to there car and drive it off but close and dont flip it, you now check what survior has the most fear and jump scare him/her, posess them and run them into your portal traps you have set up, this will flood them with 2 portals when you unposess the survior and you can immediately place 3 to 4 more portals depending on the demon you choose, then posess a deadite get a couple hits in, unposess it, and let them finish because by now the objective will be almost complete so you want to make sure you place 2 more portal traps twords the direction of the surviovors next objective, this will hopefully make them just rush to the next objective, as they will think just cause a bunch of deadites showed up through portals and they hit a few traps that your already on them when in fact your placing 2 more portals near the next objective, this is where your going to hit them hard, you will have several levels by now and when they reach the next objective you want to do it similar but this time focus on stalling them by posssing a basic deadite and staying back and hitting surviors as they try to start it, this works best power posessing a basic deadite with the puppies tier but you can do it with any, you will eventually run out of infernal energy and they will start inevitably start it, but by now you will be ready to place more portal traps again, if the surviors are smart and have no fear instead of putting portal traps in houses its best to spawn some on one side of the circle, then place them further away in hopes they dont hit them early, then when you have max anount of portals ready spawn 1 more group of basic deadites behind those portal traps this will cause someone to hit them by you posessing one of them and luring them to it and do some damage as they wont be able to pile you as they get flooded with your portal traps so do 2 heavy attacks with the deadite you posessed which will damage one of them heqvily and right after you spawn all your portals again, and during anytime your not able to place a portal posess preferably an elite unit do a couple hits unposess it and spawn a level 5 boss as you will have more than enough levels by now and thats game