Let's throw in the gauntlets to your test and assume a 4[W] power.
+6 Maul = 8d6 (2-6/die) = 4 avg/per * 8 + 6 = 38
+6 Vorpal Falchion = 8d4
2 rolls of "4" giving +2d4
2 rolls of "1"'s giving a 66% of +1d4 on rerolls
the 3d4 have a 99% of 1d4
So 8d4 just became 11-12d4 (2-4/die) 3 avg/per * 11.5 + 6 = 40.5
So the Vorpal falchion is now superior to the Maul. So a weapon that started out with a top end of "8" damage is better than a weapon that started with a top end of "12".
So, under near ideal circumstances (Gauntlets of Destruction, 4[W] attack) and with a demonstrably better weapon (vorpal vs. nonvorpal), the falchion, which started 2 points behind on average damage, has snuck out to 2.5 points ahead.
I'm not concerned.
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gnfnrf