You can't dualwield the mace as it lacks the [light] tag. I included it as a reference point, since it is the hardest hitting one-handed weapon. It was to check if dual wielding is worth it, compared to other options. Thats why I included the Bessy Mauler and Griefmaker as well.
You can actually swap all your equipped gear mid combat, without wasting a turn. This is highly relevant for the corrupted dawnsword. When facing enemies weak to blight use the CDS, when they are resitant to use something else, swap weapons. So you could use the CDS as main and swap to the petal when fighting demons.
The best dualwield option by far is the Chrysanthemum petal in the main-hand and Kunai in the off-hand. Since the petal is a thrown weapon it can use both range and melee powers, plus it it ignores the flight melee accuracy debuff. The real kicker here is the bless on crit from the petal and the bleed from the kunai. The bless effect increases the bleed damage, but the stat reduction from the kunai being in the offhand does not decrease the bleed dmg. Turn 1 you use sure shot. You crit and the petal applies it's blessed buff and the Kunai gains the higher bleed from bless instantly. The actual dmg of the weapons itself doesnt matter in this case, but the bleed outdamages pretty much evertything.
To put the Examples in Numbers: The Petal would do 58 dmg on a crit plus 12 from the blessed kunai and 37*2 from the blessed bleed. Even without the Kunai critting as well you did 107 dmg with only one sure shot. Plus 37 dmg of the second bleed proc. If the Kunai crits up the bleed to 60*2. Btw. Sure shot has a cooldown of only 1 round. The next turn you can either swap the kunai for a stronger offhand weapon, since the bleed won't stack or even replace both weapons and do a bless buffed attack or power. Turn 3 sure shot is ready again, so you can repaeat the kunai+ petal combo.
IIrc correctly the most busted dmg build is 17 strength, 17 willpower, 17 agility, with charge weapon, sure shot, song of storms and deadly shadow. Turn 1 kunai + Petal sure shot. Turn 2 Song of Storms which gives spellpower as storm damage to your weapon on a 1 to 1 ratio. That means the bless buffs gives another +100 storm dmg for free. Turn 3 deadly shadow. That is an AoE and encounter power. Since cleave and crowd control are recharge powers you can't fit them in. On top of ALL that you get the charge weapons dmg, which scales if spellpower.
Keep in mind that stances activate automatically, so the bless won't increase charge weapons buff. (Not true, bless affects active weapon buffs. Credit to
@Baggrin for pointing this out.) Using gear that increases spellpower is more beneficial for this setup, since it boosts both charge and song of storms.
Edit: In case you don't want to swap around gear or don't want to use the most busted killer combos: For main-hand always the petal for bless buffs and the utility of a thrown weapon. The occasional bless is a nice boon, even without sure shot. Off-hand Dawn Sword as it give some defensive stats as well. And of course the holy dmg.