With recent changes in wd-11 (<BoundaryDefinitions>) TOSCA provides a powerful way of composing ServiceTemplates based on requirements/capabilities. So one ServiceTemplate for a certain group of nodes can be created and re-used in larger context.
The TOSCA spec also includes a <GroupTemplate> element for grouping of topology elements.

It would be desirable to only have one way of grouping elements for re-use purposes. Since the new concept based on requirements/capabilities and BoundaryDefinitions is more powerful ad has clearer semantics, I would propose to remove GroupTemplate. This simplifies the spec and avoids alternative ways of grouping things.