Maul applies a stacking -4 accuracy to every attack after the first. It's possible that the unit you were attack had such a high dodge that it was impossible for you to hit after the first swing. Do you have any other items with Maul to compare the hit chances to?
As to your second point, Double Strike (and every other activated ability) is not considered a standard attack. The only thing Maul will trigger from is a standard attack (meaning right-clicking your enemy), as it should be.
I had 37 accuracy, the mobs i tested again (tested it in 3 combats to be sure) had 3-8 dodge.
As for the Standard Attack.... Thats not what maul says 
... That was my point anyways, that either they should make it work, or fix some tooltips.
Sincerely
~ Kongdej
