Average build for ninja is 12 str 27 agi, from what i heard, and they use 4 ps 9 athletics.
If you want to play 1h without shield, the only advantage i can think off is more agi. I already tested 2 ps 6 str 33 agi with Niuweidao, and it was ENOUGH to not bounce off at the time due to very high speed bonus. If you are going to heirloom Niuweidao, it is even more viable.
Now, why Niuweidao?
Answer is simply: only 6 str requirements.
Look at this builds:
Ninja (average) build:
Level 30 (4 420 577 xp)
Strength: 12
Agility: 27
Hit points: 49
Converted: 8
Ironflesh: 1
Power Strike: 4
Shield: 0
Athletics: 9
Riding: 0
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 9
One Handed: 1
Two Handed: 181
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1
1h ninja build:
Level 30 (4 420 577 xp)
Strength: 6
Agility: 33
Hit points: 41
Converted: 8
Ironflesh: 0
Power Strike: 2
Shield: 0
Athletics: 11
Riding: 0
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 10
One Handed: 190
Two Handed: 1
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1
As you can see, it is much faster. MUCH faster. Why MUCH? Simply: average player has about 6 athletics, better in manual block players has often 7 athletics, and you have big advantage of 4(!) more athletics and 12(!) more agi.