You can keep raccoons out. I live in the mountains, in the woods, with raccoons and all other manner of predator lurking around the coops every night, including bears, cougars, foxes, coyotes, coons, possums, hawks and the ever present roaming domestic dogs. I've never once lost a bird to a predator. Building a predator proof coop and getting them into it before dark, not letting them out until daylight, goes a long way toward keeping this from happening. The coop windows all have hardware cloth screens attached with screws backed by washers, not stapled. Only one window doesn't have it, in a building not originally built as a coop, but it's a small window high up in the middle of a wall and is closed down at night. Between the alert roosters and the buildings built to keep out chicken-eating varmints, we've dodged out bullet for 9 years of owning chickens in our predator rich environment. So, it is possible to up your odds of having your chickens safe from raccoons, even at night when you are sleeping. Remember, though, that raccoons are VERY strong. They have unexpected pulling power and are very determined.
I expect that one day I will lose a bird or two to a predator, but I do most everything in my power short of keeping them inside all day to prevent it. NO chicken wire will keep anything out.
I don't know why your birds are dropping dead. You'd have to have a necropsy done. With predator attacks, they are probably very stressed.