For raw data, here is the pool of available abilities the Lich King raid deck can use.
Necrotic Plague is a dot that is most useful later in the game if you've sent a lot of allies to their graves. It will be most effective at dealing damage to the hero with as many allies in the graveyard as possible. The rules state you can examine the graveyard of any player at anytime- so examine those graveyards periodically and start dealing damage to people this way. If you play this card right, you are getting a lot of reward for a cost of 1.
Infest is primarily a card for popping allies with 3 health or less, which is a large pool of them. I can't see any point in playing this card on one of your own allies. If there is an extremely annoying ally putting out a lot of power on the board, Infest it and make the owner discard a card in the process. Always a bonus for a cost of 1. Quake is one of two of the Lich King's instant abilities. If one of the raiders is about to zerg you with allies, or you want to stop a large weapons swing, play Quake to exhaust all opposing cards. I don't see much of an advantage to using this card during your turn.
Pain and Suffering... boy have I had a lot of that during my life. Anywhoo- and I should enter this as errata to my chart- this is another instant ability. This card is mean- and expect it to be targeted by the raiders quickly. This is a debuff to attacking allies. If you wish, you can destroy the card to fling 4 shadow damage at each opposing hero. So with a max of three raiders, you are dishing out 12 damage total across the board for a cost of 2. There are only two of these cards, so I would refrain from flinging the damage and keep the allies locked down with the debuff. Expect the raiders to try and deal with this card as a priority.
Soul Reaper is the Lich King's interrupt card. Save this for huge plays, because you only get three of them. The bigger the cost of the card you interrupted, the more resources you just stymied from the raiders- and healed yourself for. This is the Lich King's only, one and only way to heal himself that I know of. Use sparingly. Defile is my favorite card out of the raid. Raiders discard a card, turn over a face up resource and destroy an ability AND equipment. This is a sweeping board changer that helps "push the fridge off the cliff" so to speak when you need an advantage. Chances are good this card will be interrupted.
Raging Spirit is your ally hijack card. Use this card on powerful board changers or allies with big stats. The ongoing trait will give your new scourge ally assault 2 (+2 ATK when attacking). Finally we come to Remorseless Winter. Play this card only when you want to severely lock everyone down, as this card is prime for interrupts. For the cost of 3, you are dishing out a whopping 20 damage. Adding up the hero's totals, that's around 20% of the raider's collective health pool. Let them think that it doesn't seem like much- but it will become a major hassle if that card is played. Count on it to be interrupted. If you want to bait the interrupter, try playing those cards above with the least cost and get them by dropping Remorseless Winter OR one of the big ally cards from the previous article.