I have noticed quad maces sometimes have done lower damage, since asura also relies on your ATK. I think the ATK on the Garm Claw is over powering the ATK the mace gives (which renders the AK cards less useful). Basically you would need to have enough str to make your ATK when equipped with a mace to make the AK cards increase that damage past your Garm Claw's damage. Going to give an example:
Asura Formula:
[(Weapon ATK+Base ATK) x (8 + SP/10) + 250 + (150*SkillLV)]*Card Effects
Now my Champ with:
82+18 str
1+8 agi
46+6 vit
35+16 int
96+19 dex
1+3 luk
Has 375+56 ATK with Blessing, DI Ewe and +8 Garm Claw[AK]. With a +10 Mace, his ATK is 265+20. Also his SP is 752. Now lemme plug in the stuff (I'll just be adding the numbers in the ATK together with this):
[(431) x (8+ 752/10) + 250 + (150*5)]*Card Effects
[431 x (8 + 75) + 250 + 750]* Card
[431 x 83 + 250 + 750]* Card
[35773 + 250 + 750]* Card
36773 * Card
So with my current stats and equip my +8 Garm Claw does 36773 Base damage to MvPs (I am not going to include a card effect into Garm Claw to mimic your damage to MvPs)
[(285) x (8 + 752/10) + 250 + (150*5)]* Card
[285 x (8 + 75) + 250 +750]* Card
[285 * 83 +250 +750]* Card
[23655 + 250 + 750]* Card
[24655]*1.8
44397
And this is what a mace does to MvPs with 4 AKs cards in it, 44397. So unless Arc-Angeling doesn't count as a boss for us, you should be doing more damage with the mace. If he doesn't count as a boss, then what you're saying about doing 10k+ more damage with a garm claw seems to make sense (since the base damage from the mace without the AK cards is 24655.