I just want to say that the game lags for me as well on the animated forest, greater vaults, and D:50. It also lags in fire and ice battle in iqd for the first few turns while everything is still alive and the berserker prince level, although the iqd level lag less so than the other instances i mentioned.
Windows 10 64-bit
AMD Radeon RX 480 Graphics
quad intel core i5 6600k 3.5 ghz
16 gb ram
1920 x 1080 Dell E2414H
Hope this helps?