This title and article are basically press copy from CA. The relevant bits with a side of sales bullshit:

if you don’t fancy shelling out the full £19.10 for all three factions, you can grab new bits for either Nurgle, the Empire, or the Dwarfs for £7.49. If you do buy just one to start off with - say, to get a feel for the quality of Thrones of Decay as a package - you’ll get a 15% discount on the remaining two packs in the future.

The move is the latest from developer Creative Assembly in a bid to regain trust with its community after a disappointing DLC release in Shadows of Change and a series of PR blunders.