They're taking the same approach Riot did, which was to promote the growth of their casual fanbase before moving on to competitive balance.
I don't like it, personally speaking, but it's a good business move.
It's more important for them right now, as a relatively new and experimental approach to creating games (for Blizzard), to make sure their game maintains its momentum and gets enough players to be financially profitable than to promote a healthy competitive environment. And the easiest way of accomplishing that is to nerf "unfun" strats that dominate the low levels.
That said, the balance issues between classes at high levels are more or less staring them in the face and not so much as a comment, which is rather disheartening.