gzt: You would need a dock for dual ext dvi monitors on surface book. Only one DP port. But if the dock is the source of the problem maybe there is some possibility of using a better 3rd party dock.
Btw just noticed MS offer a free adaptor for SP4 to use the SP3 dock. Old style Sp3 dock has only one DP port so does not help this topic.
Yes it does potentially help. You can use the one DP from the dock to drive one screen and the DP port on the PC to drive the other.
We use this configuration for dual monitors with our two SP3 machines and it is much more robust than using the newer 'cross your fingers if it is going to work' SP4 dock with the dual DP out.