Activiti or other BPM vendors are supporting multi-instance for sub-process.

As I understand, camunda only support multi-instance in task level. Also implementing of this features is very hard.
And camunda is not yet supporting "loop" either.

It is used for creating For-loops and For-each-loops for iterating through Arrays. In the
BPMN model, a multi-instance activity (for or for-each loop) is indicated by a multi-instance marker (three small parallel vertical bars – horizontal for sequential and vertical for parallel) overlaid on thesubprocess activity