Just forget it. Currently game mechanic doesn’t allow that.
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Besides, let me remember how DW Cadence works:
As known dual-wielding allow chance to hit with main hand, off-hand, or both. Same is true for Cadence discharge (I don’t use 3rd strike term due to the following). So, when you discharge Cadence with both hands, as known only one weapon deal full damage, but second one counts as basic attack and charge your next Cadence. Moreover such attack can prock WPS. Thus with enough of luck you will have Cadence discharge each 2 attack.