To answer this, we simply need to look at how the penetration passive from Maces/Mauls are calculated.
For Maces: (18,200-(Sum Of All Debuffs))(.1 x 2)
For Mauls: (18,200-(Sum Of All Debuffs))(.1 x 1)
As you can see the penetration applied by Maces/Mauls comes AFTER debuffs.
Why is this an issue?
Let's look at different scenarios, note that Alkosh penetration values/penetration values in general have been even more upped post-Markarth DLC/Update 28:
1,170 Penetration is gained from Maces/Mauls.
1,982 Penetration is gained.
2,584 Penetration is gained.
3,640 Penetration is gained.
In even the least organized groups, it simply is not a great choice for DPS when compared to the damage gain from Swords, the bleed from Axes and the crit gain offered by Daggers.
So how do the different weapon types rank against each other?
Dagger is going to be the strongest, providing roughly 3 to 3.5 percent more damage. Swords will typically provide an additional 2 to 2.5 percent more damage.
Axes, therefore, need to deal more than 2.5 percent of your DPS to be worth running. However, running dual axes is not advised since you cannot "stack" the bleed procs from both.
Maces are simply not worth running in organized groups.