My damage is around 2.5k but when my fan of knives successfully hit enemy. My overall damage reduce to around 1.6k and slowly increase back. Is the skill meant to be that way?

Oh.. Not only fan of knives.. Don't know how my skill works.. 

I only find Nightmare easy once my DH hit 14k hp and 12.9k DPS
.....and even that I'm now struggling in Hell Act 1. 

How much? american server?

plenty room for improvement, if u noe wht i mean

what gem to use for weapon? considering emerald to increase crit dmg. or ruby better?

sigh, sacrifice alot last nie..
for 110500 DPS @ 3.08 AS - Dual Handed Bow

my health become 16k

yup..
without sharpshooter 62k DPS @ 3.08 AS
fark, how to reach 200K DPS..
jelly @ Athene, he so easy get gold..
i farm like hell only can get 5m     

Bows anyone? Need to clear my stash. Add cornflix#6757 for fast deal.

You shouldn't have any problem with killing Butcher alone as a DH.

Yeah, Act 2 memang like that one. Expect to die alot. I mean A LOT. I just freaking grave zerg-rush the entire act.
Those Lacuni and Vipers are annoying as hell.

I skipped most of act 2 elite mobs when i see them. Just finish the quest and kill Belial asap to proceed to next act and never look back.
It is not worth your time to farm Act 2 since their loot table is almost the same as Act 1.

Act 3 is definitely easier than Act 2 and has better loots. The only thing you need to worry in Act 3 is those long tongue mobs (Soul Lasher/Ripper) and the Phase Beasts.