Hi Ahri,

don't be sorry for asking. Better safe than sorry, right?

Now to answer your questions:

First things first: Dark Mind doesn't need Dark Arts anymore, it provides 30% magic mitigation on default now!

For single target:
Dark Passenger only in opener (overwise you cap mana), if you don't have any slashing debuffs (WAR, NIN or SAM in party) AND are MT you can use it on CD.
Carve and Spit always with DA enhanced!
Delirium always with Blood Weapon - inital MP gain is the same as Blood Price, but you generate more MP with Blood Weapon on single target.
Don't bother with Quietus on single target, focus on Delirium and Bloodspiller.

This should be your lvl 60 MT opener, this one as OT

For lvl 70 openers here

On trash, you use CnS without DA for MP gain, Quietus (with DA if you can afford it), Abyssal Drain (with DA only if you would/are overflowing with mana), don't bother with Sython Strike - unless you are starving.