Why everyone believes Lich King is more powerful? I get that 8/8 taunt is good and ysera May stay passive in the board but isnt Ysera cards are much more useful?
The only bad ysera card is laughing Sister and it is a 4 drop value for 3 mana. But ysera awakens, dream and the zero mana buff are all pretty successful.
On The other hand Lich King cards are too situational. Army of the Dead is a yolo card. Can screw you over. Death grip is meh unless you play against a combo deck and steal something good. Removals are too costly and kinda useless if you are winning already. Death and decay is probably the Best one with 2 mana deal 5 being the second Best. But neither of them is a ysera awakens
Lich King cards are situational, but each is exceptionally powerful and game changing. Ysera's are similar but to a different degree. Lich King is a taunt, which adds protection to your face - and big synergy with certain other cards like Hadronox Lich King is cheaper Lich King deals more damage.
Dont disregard the difference in mana and the fact that LK is a taunt. These two factors alone make him a much bigger problem to deal with.
So, The Lich King is 8 mana, that means you can play him earlier and it lets you hero power ( or play a 2 mana card ), it’s a taunt and has 8 attack so it’s a huge threat in many different ways; out of all his cards army of the dead and doompact are the less situational, but all the other have great value, anti-magic shell is very strong even on just the King alone, death grip is basically like Gnomferatu but you get the minion, obliterate is very good, death clois is either damage or healing so very versaitle death and decay is crazy good and frostmourne can have amazing value ( or 15 damage to face ) but with some classes and in some cases you can’t use your health, and it costs 7 mana which is a lot.
Ysera Is 9 mana, wich is worse, has only 4 attack so it’s not a huge threat but the 12 health and effect makes it a soft taunt, it helps with dragon synergies both with itself and the emerald drakes you can get, but the other cards you can get out of her are somewhat worse than the Lich King ones, nightmare is strong but only as a finisher or as a delayed deathrattle enabler ( anti-magic shell is better ) dream is good if used for a combo with your won minions but it’s just a minor slow if used on the enemy, and finally ysera awakens also damages your face so it’s strong but with a downside.
Very few cards costing more than 4-mana see play if they don't immediately impact the board. HSReplays posts a list of the 100 most-played cards in Standard - apart from Genn and Baku, which are special cases, there are only three cards on the list above 4-mana which don't actually do anything the turn they are played.
Too often, Ysera can be a dead draw - you can never play her if the opponent has lethal on board. She doesn't ask the opponent any questions the turn she hits the board, while the LK has to be answered - it's also worth pointing out that his 8-Attack is actually a pretty big deal, given that a number of his DK cards are direct damage.
The Lich King is an Ironbark Protector which ain't bad for a vanilla card in the first place. Furthermore, being a Taunt minion your opponent needs to trade off his board in case there's no removal. Ysera is a Sleepy Dragon but without Taunt which makes it very awkward to play. Regarding the Dream cards, Dream, Nightmare and Ysera Awakens are strong but certainly not game-ending since Ysera is usually being used in Control decks. Also, Laughing Sister and Emerald Drake are nothing but a huge pile of stats. On the other hand, Anti-Magic Shell or Death Grip (in case you're up vs. a Combo deck) can spell instant win. And the power of Frostmourne or Death Coil isn't really up for debate either. The only thing you might argue is that the chance to get the right Death Knight cards is much lower.
Remember, even old Dragon Priest lists mostly didn't include Ysera for a reason. But she's an evergreen card and without doubt no bad choice.