How to skip requester in approval flow for Performance Document approval task?

Summary:

According to our customer requirements, Performance document should be sent for approval to the Head of Department and then to HR Director.

But in the situation when Head of Department is a requester (so he realizes evaluation for direct employees), this approval should be skipped and go directly to HRD.

I've tried the following configuration but it doesn't work:

BPM Worklist -> Task Configuration -> PerfDocApprovalTask

In Configuration section I've activated the "Prohibit self-approval by users named in these payload attributes" and tried the following payload attributes:

1) /task:task/task:payload/ns1:TransactionApprovalRequest/ns1:requestor

2) /task:task/task:creator