Currently, for some reason root is being split even if theres only single node, moreover, some nodes are also split. 
https://gist.github.com/DarkDimius/bfad187a562caec061c7 - here is log for single thread. Worker works on 4 different nodes.
I've fixed it for Sequential scheduler by explicitly assigning invoker as an owner of root. 
But we probably should investigate deeper.