I have checked on this earlier, before it changed to dmg reduction from armor increase. For example, we had a really big difference in damage on the main tank at hodir from one week to another. The first week I had been healing the tank and the uptime of Inspiration was pretty high. The week after it was a pvp-specced discipline priest who had healed the same tank and he then got inspiration just occasionally from the holy priest. But we weren't sure the big difference could be explained just by the uptime of inspiration.
I'm afraid I don't have so many new examples, I have been holy in many fights recently, but from last week I have Northrend Beasts, where I was on tanks all the time, but since the were switching between who was maintanking all the time, it's not a that good example.
Tank1: Inspiration 23,3%, ancestral fortitude 45,8%, total=69,1%
Tank2: Inspiration 29,8%, ancestral fortitude 24,5%, total=54,3%
So not so high I guess...
Now I found an old Hodir example, where I was focusing on the main tank:
http://www.worldoflogs.com/reports/wabf ... 12&e=11442There you can see that the uptime of Inspiration is 65,9% and ancestral fortitude is 24,5%, so then it sums up to 90,4%.
(Not so proud of my uptime of Weakened Soul though).
You should find some other examples if you check the same raid for other bosses, like XT-002 Deconstructor (uptime for I+AF >75%), Ignis (uptime for inspiration here is 70,5% and AF is 16,9%)