|Yeah, I hate them too.|
I apologize for the no-post yesterday- it was my birthday.
Grey Knights ought to be an auto-lose for Daemons- I mean, not only is Grey Knights the newest Power Armor Mat Ward Codex, and Daemons are the 4th ed. rejects, but Grey Knights are unashamedly specifically designed to kill Daemons!
However, it's not that straightforward.
Daemons actually negate many of the smaller advantages that Grey Knights hold, namely, their universal Nemesis Force Weapons are largely ineffective- oh sure, the leadership-check-or-you-die is there for Daemons, but power weapons are considerably less helpful, and the Force Weapon quality is completely worthless. They pay points for this, and the fact that it doesn't help means wasted points for them.
However, they have some other tricks. Hammerhand is a pain across the board, though at least S10 daemonhammers aren't that big a deal. Re-rolling against us is another insult to injury, but despite all this, Daemons still dominate close combat. And do you know why?
Invulnerable saves. Where Grey Knights have them, they pay for them, and usually something else too. Terminators pay for their armor, which daemons ignore- that 5++ isn't worth 20 pts, that's for sure.
For Daemons, not just in Close Combat, but the whole battle, It's all about removing points efficiency, ignoring things that Grey Knights pay through the nose for. Paladins? One Bolt of Tzeentch insta-kills one. Purifiers? Flamers of Tzeentch will destroy the entire squad in one burning.
And Grey Knights often fail to take advantage of one, vital weakness of Daemons: Heavy Armor. Grey Knights rarely bring Land Raiders, usually opting for the flashier, faster Stormraven, and this is good- it pays for melta immunity (ignored), it's two anti-tank heavy weapons (largely worthless, and if it goes for anti-infantry... still worthless, nobody's scared of a heavy bolter, an assault cannon and maybe more bolters) and all it's other special rules, but at the end of the day, a properly equipped Daemon army can handle an AV12 vehicle, and there goes your 205 pt flying brick.
Everything that Grey Knights get is expensive, because they have something that they pay for- ignore whatever it is, which daemons CAN DO, and watch the army crumple.
Does it shoot? Kill it with bloodcrushers. Does it assault? Kill it with flamers and chariots. Does it do both? Your opponent payed way too much for it, do whatever it sucks at (protip- it sucks at something, there's no such thing as a unit that's legitimately good at both)
Oh, and keep your Soul Grinder in the back, Phelgming anything with a 3+ armor.
For Grey Knights... honestly, you don't need a tactica. You're Grey Knights versus Daemons. Figure it out.