Would Eberspacher Easystart T Timer require a separate temp sensor with a non H-kit airtronic D2?

Yes, an older generation pre H Kit Airtronic will require in addition a method to control heater output according roomn temperature. You would require an additional temp controller such as the Eberspacher mini controller 221000320700. Plus if you wished to reference room temperature to control heater output (rather than the default referencing via the heater air inlet temperature) then you would require to fit a remote temp sensor also.

Regards

David