Hmm, I did some reading on Elitist Jerks over the weekend and they seem to think that the Moonfire idol has a 50% proc rate instead of 30% as I originally thought. This changes my figures quite a bit. (Also, the SF idol is 55, not 57 - shows what I get by working from memory).
MFx1 SFx3: MF Idol 66.9, SF Idol 40.4
MFx1 SFx4: MF Idol 52.3, SF Idol 55.9
MFx1 ISx1 SFx3: MF Idol 57.5, SF Idol 35.4
Based on the above results, the Moonfire idol is clearly superior in most rotations.
I'm still not sure on its benefit vs. the Raven Goddess, though. Let's take the optimal rotation with 67 extra spell damage on average; that's 67/3 * 1.2 * 1.1 * 1.3 (crit) = approx. 38 DPS - call it 35 with Moonfire having a lower coefficient.
The extra 0.9% crit from the Raven Goddess increases DPS by approximately that amount; let's work that with various average DPS figures from each party member.
1000 ea * 0.009 = 9 DPS x5 = 45 DPS
1200 ea * 0.009 = 10.8 DPS x 5 = 54 DPS
So, the Raven Goddess comes out ahead when you consider its benefit to the raid as a whole, and the fact that its effect increases as the DPS of the party goes up, whereas the Moonfire idol has a static benefit based solely on the ratio of Moonfire in your rotation.
Edit: Fixed Starfire calculations... again.