This post will be updated with May hotfixes, with the most recent at the top.
Hotfix 3 (v12.05.3)
(June 30)
Balance:
Redraw (in PvE only) 
Redraw cost doubled
We’re happy with the recent changes to PvE, but Redraw’s ability to access certain combos is too strong.
Mastermind Rolls 
You are now guaranteed 2 DPS of different types (up from 1)
You are now guaranteed 2 tanks of different types (up from 1)
Responding to community feedback about wanting more reliable rolls.
Wave 6: Rockos
Impale: Max stacks against the king: 4 → 3
Now less lethal against the king.
Wave 15: Quadrapuses
Health decreased by 1%
Wave 16: Cardinals
Health increased by 0.9%
Wave 17: Metal Dragons
Health increased by 1.4%
Wave 18: Wale Chiefs
Health increased by 0.6%
Autoattack damage increased by 1%
Shifting power from wave 15 to 16-18.
Hotfix 2 (v12.05.2)
(June 19)
Balance:
Lock-In
Improved Auto Draft, since it became a little worse due to the recent Mastermind Roll changes.
Improvements:
Classic PvE
- The sending AI is less likely to income send, and also won't send Hermit before Wave 5 because it's just worse than Brute in a lot of cases.
Fixes:
Some description fixes
Hotfix 1 (v12.05.1)
(June 18)
Balance:
King Upgrades - Upgrade Attack: 14% → 12%
- Upgrade Spell: 7% → 6%
Reverting King Upgrade buffs from 12.04.
Improvements:
Classic PvE:
- The sending AI is more likely to income+king, resend, and save for multiple saves in a row. It's a little too predictable right now.
Fixes:
Some description fixes