[Gozuk]

I would say if you're mainly swapping to the Swarmcaller/Runed blade to proc, then back to whatever/Swiftwind (you have SW right?) to dps, not to worry about a backup haste item. From what I understand you would have a better chance at procing those weapons minus the haste. Hiero cloak or Lodi shield may be better options for your back slot. For the price, the RBG is a great item to wear regardless if you're using the haste or not.