Disagree with you Hoover.
Houston and Dallas are not the same market - so your Bay Area/LA/NYC/Chicago analogy does not apply.
Its geographic proximity that matters, not being in the same market. The best examples here are the 2 Florida teams and the 2 Missouri teams. Notice, they're in different leagues. The MLB wants people in those states to be able to see both leagues and be within a reasonable distance I imagine. The only exception to this rule in all of the MLB is the 2 NL teams in Pennsylvania.
Moving AZ or COL to the AL West, then Houston over to the NL West (leaving the Central with only 5 teams) makes the most sense.
The best solution would've been for Tampa Bay or Florida to move out West, but thats not happening now. I would've loved to have seen a team in Vegas (or Portland or SLC) for instance and then the Pirates could've moved over to an Eastern division, but the Florida teams seem secure in their locations now for the foreseeable future.