You're still able to be interrupted when casting, still able to be CC, etc.
For a 2 min CD that only lasts for 10 seconds, Shamans basically feel this is not a top end product for a so called 85. people already can cast on the run, best example is a Fire Mage. Spiritwalker's Grace needs a tweak, but not something that can make Shamans too powerful. AKA: don't make it an OP ability that the class is balanced around.
1. Change this ability to a 45 second or 1 min CD.
2. Keep at 2 mins, but also puts a protective barrier around the Shaman to prevent all silence and interrupts through the 10 second duration and allow the Shaman to cast on the run.
3. Keep at 2 mins, but increases spell haste/casting by X% while under the effect of Spiritwalker's Grace and allow the Shaman to cast on the run.