After only a couple of loops using found Fort. Alchemy gear, the Amulet of Talos Bonus and Shrine of Talos bonus gets me down to 11 seconds for a Fus Ro Dah. Most of the other shouts, like Slow Time, Marked for Death, Elemental Fury, etc. are so short that you can use them with virtually no delay.
Since shouts are an integral part of my current character, I've come to the conclusion that 50% cooldown reduction is the sweet spot. Its fun, but not too overpowering for enemies, especially considering my weapons paylod of an Exquisite Silver Sword and Exquisite Imperial Bow + Orcish arrows.
Thoughts?