Its from Elitist Jerks, do a quick search on these forums, its referred to more than once I believe.
I found that in the quick ref guide. I can't quite seem to find the link where this is spelled out however. Does anyone have a link to a guide that shows how this was determined? Thanks.10. On bosses, Improved Demoralizing Shout is not effective past 2 talent points. This is a significant change related to Attack Power values in Burning Crusade. However, in situations where Curse of Recklessness is applied to the creature, the full 5 points will be effective and will negate the additional Attack Power.
Thanks, I'll take a look. It's funny since the discussion I saw of why to use 5/5 imp demo shout was _also_ from EJ's forums, although it was a pre-BC link.
You're looking for this thread: Curse of Weakness - Elitist Jerks (check the second page).
And yes, things have changed quite a bit since level 60, where Improved Demoralizing Shout was the best damage mitigation talent a warrior could get.