Pirates not only killed all the fun for Hearthstone players but also had a major impact on the revenue Blizzard got in February. SuperData's report shows that mobile revenue (from Android and iOS devices) is at its lowest point since the launch of the game. Both year-on-year and month-over-month figures are down significantly. This is to be expected as the main hook of Hearthstone is its fun gameplay, and the gameplay players experienced was nowhere near the word fun.
The desktop version the game also experienced revenue cuts, but not as severe as they were on mobile devices.
Blizzard is slowly improving the situation. The company has released a patch that aims to fix the gameplay problems, plus the game is said to have its next expansion released at the beginning of April, maybe even next week. So, things aren't looking as grim as they may seem to be if you check SuperData's report name, "Hearthstone is killing itself".
However, we think that the Gadgetzan expansion, and the situation with the Pirate archetype, will definitely be remembered by players and developers. Blizzard will probably be more cautious with new mechanics and Metagame shifts in the future.