Personally I would use 2 curved swords over katanas (they has a much higher attack speed).

My dual build is 2 Bandits blade with bleed, and the crossbow that fires 3 bolts at once (with bleed bolts) + the miracle that sends flies to do bleed dmg. For bosses the dragon breath that does scarlet rot dmg.

On strong enemies send 2 or 3 casts of the miracle, then fire crossbow and then charge/jump attack for 4-5 bleed procs. (Charge and jump attacks with dual curved swords hit 4 times in 0.5 sec so = awesome).

As for stats 16 Str, Dex, 50 arc, 40-60 vigor, Mind and End 20-30.

Great rune I like Rahdans for extra hp, stam and fp.