We have crossed the line of balance between 2h and slashing polearms. Now GLA/LHB twister spam works better. In the following text, 2h means all weapons with side swings, without shield.
I think the very early learning curve is way steeper for 2h than 1h. When you don't know how to block, 1h will clearly work better.
But after a while, as everyone improves, it becomes harder and harder to play with 1h + shield. Your main advantage of not caring about blocking becomes less and less important since many 2h learn to block very well (it's easier with the autoblock hack btw
). It goes down to a point where improving as a 1h takes tons of hours playing and being very skilled, compared to 2h that just have to take the full advantage of speed, damage and reach. A 2h will likely start to defeat an equally skilled 1h very soon after having mastered blocking. The all rounder 1h is inferior to the all rounder 2h in all ways. While this was perfectly logical during the first months of Warband MP, now it's a problem because the shield doesn't help so much in melee as before.
But this is only about duels. 1h got an advantage with defending against range (not attacking since attacking range usually means being ranged yourself) and can fight multiple opponents with more ease than 2h. They are disadvantaged against cav though.