I have played them a few times and most players will have a good amount of magic and at least one big guy. They will more than likely have a herald with a nasty banner as well. Getting in combat and flanking is one thing but not easy to do. One should also have long range weapons and shoot them as they advance, Screamers can be very nasty when they fly over you and cause damage just for that, shoot them down early. I have played tzeetch with a lord of change and lost but still managed to leave with dignity by taking down a herald on a chariot as well as screamers and some horrors, I have also played a combo army of tzeetch and Khorne with a bloodthirster that simply kicked my butt. One was with dwarfs and the other was with high elves. The daemons are a very strong army when being played by an experienced general but I know one day I will beat them.
