DNC's Sambas already gain 'potency' over Melee/DNC via increasing levels:
DNC can use Drain Samba III. /DNC is limited to Drain Samba II.
DNC can use Aspir Samba II. /DNC is limited to Aspir Samba I.
DNC's Haste Samba grants 10% JA Haste with 5/5 merits. /DNC Haste Samba is limited to 5% JA Haste.
DNC's Sambas, when used with Dancer's Tiara, last 30 seconds longer than Sambas from /DNCs.
DNC's AF3+2 Set Bonus allows DNC to occasionally deal double damage with an active Samba, and that's the case a majority of the time. A /DNC melee can't do that.
DNC's Waltzes also already gain 'potency' over Melee/DNC via increasing levels and through the Waltz formula:
Melee/DNC is limited to Curing Waltz III. DNC, though, has access to Curing Waltz V.
Melee/DNC is limited to Divine Waltz I. DNC, though, has access to Divine Waltz II.
DNC has access to more Waltz Potency gear than /DNC melees.
As for Steps, DNC has access to several pieces of "Increases Step Accuracy" gear. /DNC melees don't have access to that gear. Also, /DNC melees can't use Feather Step.
Melee/DNC are limited to one Finishing Move per Step. DNC get two Finishing Moves per Step, and if they use Presto, DNC can get three Finishing Moves per Step. By way of merits and Charis Bangles +1/+2, DNC sees much higher TP returns from Reverse Flourish than /DNC melees
and DNC can build 5 Finishing Moves with only 2 Steps.
With Etoile Casaque, DNC's Violent Flourishes are inherently more accurate than a Melee/DNC's Violent Flourish.
With Dancer's Toe Shoes and Etoile Tights, a DNC's Spectral Jig is boosted from 30 seconds to 90 seconds. A /DNC melee is limited to a 30 second Spectral Jig
and /DNC does not have access to Chocobo Jig.
Should I continue?
EDIT: Continuing!
Here's a list of DNC's Job Traits*, all of which are more potent than those granted by /DNC:
Dual Wield IV
Subtle Blow IV
Accuracy Bonus III
Evasion Bonus III
Skillchain Bonus IV
Critical Attack Bonus II
Resist Slow
Conserve TP
Tactical Parry
Closed Position (via merits)
That's
insane!
*Note: I nabbed the Job Traits list off the Wiki. It may or may not be incorrect.