JR Pass vs Individual fares

Me and 2 mates are flying into Osaka on 20/12 and are planning on being in Hiroshima on the 29/12. Between these dates we want to explore the Osaka-Kyoto-Nara area. Couple of questions:

What's the best (cheapest but reasonably fast) way to get to Hiroshima? How much is a one-way shinkansen from Osaka to Hiroshima (according to Lonely Planet it's about 10,000yen)?

We've been looking at all of the different JR passes, as well as the Seishun 18 Kippu tickets, but if the info in Lonely Planet is right, travelling between these cities is going to be way cheaper on regular trains (600yen per ticket) than a JR Pass. Are we missing anything? Even if we only "activated" the JR Pass so that we can use it for the Hiroshima leg of the trip, would we still make use of 18,000yen worth of travel on JR lines?

The shinkansen from Osaka to Hiroshima costs 9950yen and takes 1 and a half hours, if you take the limited express trains instead of the shinkansen it involves changing trains 3 times, takes 5 hours, 42 mins and costs 5460yen. So I's say the shinkansen is worth it.

Check out www.japanrail.com where you can search train times using 'hyperdia' and it gives you the cost. It also tells you about regional rail passes, for example the JR West Sanyo area pass will cover your shinkansen trip from Osaka to Hiroshima and it is 20 000yen for a 4 day pass, so if you return to Osaka in 4 days you will get your moneys worth, there is also an 8 day pass for 30 000yen.

The JR West Kansai pass is really good for travel around the Kyoto, Osaka, Nara area and also covers the limited express train from Kansai airport which is quite expensive on its own, as well as Kobe and Himeji (1 day: 2000yen, 2day: 4000yen, 3day: 5000yen, 4day: 6000yen). This pass is for local JR trains only (apart from the airport express).

Options for travel between Hiroshima and Osaka:
http://www.japan-guide.com/e/e3404.html?aFROM=2157_2160