AMD has released a brand new driver for its graphics cards. According to the release notes, the AMD Radeon Adrenalin Edition 18.6.1 is optimized for Warhammer: Vermintide 2, offering up to 9% faster performance on the Radeon RX Vega 56 and up to 10% faster performance on the Radeon RX580.
Source: N4G PC AMD Radeon Adrenalin 18.6.1 is optimized for Warhammer: Vermintide 2, fixes numerous game issues