RE: Has anyone replaced ReQlogic with Workflow in version Dynamics 2013 or higher?
It depends. We implement both ReqLogic and GP workflow for our customers.
You need to define your Requisition workflow rules and evaluate/test them against the GP Requisitioning.
ReqLogic capabilities are much more advanced.
For example, you can create requisitions for approval using "punchout" capability with RL but not GP Requisitioning.
The workflow engine is more capable than GP requisitioning but again, you need to know your workflow rules and possibly flowchart them out.
I would suggest you engage your Microsoft Partner to assist you with the evaluation.