Managed to fin a solution for this little problem I had (Failed to start game (missing executable)), when first installing the new workshop tools.

1. Opt in for Steam beta, this is done by going into "Steam" (top left corner in steam) -> "Settings" and then in the "Account" tab opt in for the Steam Beta.
2. Restart Steam
3. Force a Dota 2 update by right clicking on Dota 2 in yo u installed games list, then "Properties", and under the "Local Files" tab click the "Verify Integrity of Game Cache"
4. Wait for the 5.5 GB download to complete.
5. Go to "Library" and select "Tools", then install "Dota 2 Workshop Tools Alpha"

This solved the problem for me on Linux at least, I do not know if this works for Windows and OS X users, but I reckon that this solution should work for you as well if you use Windows or OS X.