It only makes sense, especially with how much the 2 additional seconds on Battle Cry increases our overall damage.
However, being FORCED to use 4 pieces of Tier 19 with how poorly it's all itemized is very unfortunate. I would not be remotely disappointed with this change if the importance of Mastery was recognized.
What I am talking about:
Update (4:00 AM EST): In addition to the changes announced below, the 2 piece and 4 piece set bonuses have been swapped for the following two specs: Beast Mastery Hunter and Arms Warrior. The spell names do not currently reflect this change on the PTR, but the items themselves do.