To an extent, RDM's DD potential is still good compared to other mages. I think that's where SE is content with leaving RDM for damage dealing.
Mage melee hierarchy
BLU(Thaumas, A- skill, native DW3 and Triple Attack,self haste,Almace)
RDM(Almace,20% DA from Temper,self haste, enspells,gain-str, dia III)
BRD(Twashtar/Mandau, Hecatomb gear,evisceration/exenterator,augmented sky gear,marches,)
WHM(Mjollnir, decent haste gear,auspice,hexa strike,boost-str, dia II)
BLM(Only putting them above SCH and SMN cuz they can use daggers and evisceration)
SMN(Avatar Favors can give good melee bonuses, Shattersoul is great)
SCH(Self SC with their spells, Firestorm, Shattersoul)
So when it comes to mages, RDM is one of the best meleers, it's just that when you compare us to dedicated melees, we're terrible, which makes sense cuz we can also cure, debuff and nuke whereas melees specialize in melee.
Actually BRD could potentially out damage RDM in pure melee just because of gear selection(They can evisceration/exenterator with hecatomb/genbu/seiryu gear and gets plenty of other haste gear and DW from Kirin's Osode) and give themselves close to capped magic haste too.