I really thought LoE was the start of seeing Legendaries with fun effects that are playable in some way. When they revealed C'Thun I thought, okay flavour wise good, playability fine, offers nice, though straight forward (not necessarily a bad thing), deck building options.
And then the other 3. Y'Shaarj and N'Zoth just incredibly bland and uninspired. Yogg very flavourful but completely unplayable. I really hoped that the titular gods would be something else. Just fun, well designed, unique cards that can be played in specific decks.
What a let down in that regard and a waste of the titular Old Gods.