Hello Paul,
The 7 day JR Pass certainly makes for an interesting option.
Have a look at the above ticket prices (without the JR Pass).
Kyoto - Hiroshima ¥ 11,090
Hiroshima - Tokyo ¥ 18,560
For a total of ¥ 29,650 the 7 day JR Pass is ¥ 29,110 so you'll already make savings. With the 7 day JR Pass you will have an other 5 days of unlimited travel, so it's easy to make savings. For instance to travel to Narita Airport.
I would also recommend purchasing an ICOCA + Haruka Package which gives you a discount ticket to Kyoto and gives prepaid travel card (ICOCA) which you can use to travel on local transport in Kyoto.
Hope this helps,
Daniel