Melees have available overwhelming amounts of Haste, Double Attack, and Triple Attack to increase their attack speed, but Refresh items for casters remains a cheap trickle.
How does Double Attack, Haste, Triple Attack translate into Refresh for mages? Since CoP, mages have been getting incredible amounts of "Fast Cast" "Conserve MP" "Quick Magic" and MAB gear such that almost every mage can get capped casting speed, which further makes RDM less special(RDM's special trait is Fast Cast but many mage classes can cap Fast Cast too).