The Nobushi in its current state is op. The class has 3 things going for it currently: Speed, bleed and range. There is no other class in the game that has all 3 of these attributes. (New characters?) Nerfing is not the word to use as people associate it with making the class bad. What should be done is decreases the amount of damage bleed does. The ticks of bleed should last longer but do less damage as to not take away from its ability to do more damage while bleed is in effect. Bleed also should not be able to stack as getting hit about 3 times by a bleed attack kills you (base attack damage plus bleed). If stacking of bleed cannot be taken away then the initial impact of the attack (base damage) needs to be reduced or non existent in order to compensate.

The other suggestion addresses the speed of the nobushi. This is not to be in addition to the bleed effect, these suggestions should all be decreased independently of one another or slightly toned down in each area.
The speed of the nobushi is way too fast for the amount of damage it does. The speed should be slightly reduced to be on par with the likes of the raider, who which she is currently faster than and does more damage. Her ability to attack as fast as an orochi while doing the damage of someone like a kensei . Her speed to damage ratio needs to be brought down to about raider: oroch. This should bring her inline with other champions without breaking what the champion is about.

Her range will be fine as is once the necessary adjustments are taken. As a player that has just over a 24 hours of playtime as a samurai, i can confidently say the nobushi and the peacekeeper are the only two champions that feel over powered.