I see the confusion here.
Per the content release plan here: Classic Content Plan
Phase 2 will be Dire Maul which was released in 1.3 Assuming we start at release at Phase 1 (patch 1.12 in this case), Phase 2 would include all the balance changes between 1.12 and 1.3 to account for the Dire Maul release.
BWL is Phase 3 and Patch 1.6 in classic. All balance changes on Phase 3 release should be what occurred between 1.3 and 1.6 to account for what balance was when BWL came out.
And so on…