Comparing 14 days JR Rail Pass vs. buying each tickets.

14 Days JR Rail Pass: US$ 423/person

Fare calculation is based on a routing you have posted:
Tokyo – Kyoto – Osaka – Nara – Hiroshima – Tokyo

Buying each tickets:

Under your situation if you can make the trip leaving Tokyo and arrive back to Tokyo in 12 days then that will be cheapest, because you can take advantage of round trip discount on base fare (乗車券).

Best under this routing will be buy round trip ticket as:

Tokyo –(Shinkansen)- Kyoto – (local commuter train)- Osaka –(Shinkansen)- Hiroshima – (Shinkansen)- Tokyo

To the above buy separate round trip ticket of Osaka – Nara on local commuter train.

Total of above using Nozomi will come out to 39,928 yen/person, or US$ 388.74/person.

If you ride US$ 35 worth of JR Lines addition to that then you will come out as break even with JR Rail Pass.

Cannot ride Nozomi on JR Rail Pass. Nozomi departs Tokyo every 10 min. where Hikari runs twice every hour.

Retrun from Hiroshima, need to transfer at Shin Osaka if you use JR Rail Pass because cannot ride on Nozomi on JR Rail Pass. If you buy each tickets then can ride Nozomi form Hiroshima to Tokyo without transfer.