you asked the wrong question. No one needs their dual. The correct question would have been: What makes the ESFp and INTp compatible and how does each benefit from the relation?
INTps like to study people's(and objects') personal habits and behaviours. These could concern personal economics, relationships, and anything. Who could provide more data than the ESFp?
Everyone has met their dual. You have met every single socionic type. Perhaps you haven't been close to a person of each type, but met, yes.