I found similar issues.
Do a monitor cap, not a game cap. DO NOT alt-tab for any reason.
I had to edit the registry to change the graphics settings for warcraft or it would lock up.
Then I launched the game to make sure it was running good at the right resolution.
Then I exited the game and launched OBS, set it to monitor capture.
Start streaming, then launch the game.
Alt-Tabbing kills warcraft (for me anyway)
