There’s a new, DirectX 12-focused patch out for Deus Ex: Mankind Divided today, which should improve performance for those opting to use that API. Since the changes are all DX12-related, this probably only downloads for players who have chosen to use the DX12 preview branch.
The patch notes state that this release fixes a DirectX 12 start-up crash, and reduced CPU usage when running the game in DX12 mode. It should also slightly reduce system memory usage.
That’s basically the notes in their entirety. If you have Windows 10 and a compatible GPU, you can opt-in to the Deus Ex: Mankind Divided DirectX 12 preview branch by right-clicking on the game in your Steam library, opening up Properties, finding the Betas tab, and choosing the appropriate dx12_preview branch from the drop-down menu.
All prior patch builds can also be found here, in case you want to revert to an earlier version of the game.