You may want to try a clean install of Mosaico. Please follow these steps:
1. Uninstall Mosaico
2. Reboot your PC
3. Delete Mosaico installation folder (i.e. C:\Program Files (x86)\Mosaico). Your settings will not be deleted.
4. Install the latest version of Mosaico again.

If you still encounter the problem about the missing dll, please install this package of Visual Studio 2015 dlls:
I hope this proves helpful. Thank you for reporting this issue, I’m going to check the installer to ensure that no dlls are missing from the default installation.