I'm not entirely sure how great ArP is, but I know for MM and SV hunters you WANT to get haste up until you have 15.94% haste (or 523 haste rating). While yes a shaman could bring us up to that amount with windfury totem alone, I would not count on having an Enh shaman (or even 2 caster shamans, 1 for caster totem and 1 for physical) in every raid unless you're in 25-mans or have a set group WITH a shaman that will drop your totem. This gear has 204 haste on it, so getting the 10-man set gives you almost 2/5 of the haste needed, before gems.