You're missing the point. There are haste caps that are specific to SotF. The point is that you should never reforge for them.
Then you'd gain far more by using Wild Growth more than you'd gain from reforging. On fights with constant incoming damage, you should be glyphing WG and using it on cooldown, while saving Swiftmend to use it with every other Wild Growth (using it just before WG comes off cooldowns).
Either way, more haste won't help you if all you get is a SotF breakpoint. There was a long thread on the subject a week or so back. Aside from 3k and 13k, reforging to haste is not worth the loss of mastery or crit.