If the IRA contributions are already reflected in the W-2 do they still need to be listed under deductions and credits?

No, if the retirment contributions are already reflected in the W-2  then you do not need to enter them again under deductions and credits.

Unless the code in box 12 of the W-2 is code F or code S, your contributions are not to an IRA but are instead elective deferrals to a qualified retirement plan like a 401(k), 403(b), 457(b) or the federal TSP.