Damage over time effects work in a particular way. It takes your current crit chance into consideration when it tics, not before you cast an ability.

So you actualy want to use Shadowy Disguise after you applied a DoT effect to your target. This way you can automaticaly crit with a specific effect while cloaked.

Works very decently with skills like Bloodcraze, Soul Tether, Rally, ...

Edit: sorry... my initial response to the OP topic got buried in all my opinions!
Short version = I'd suggest using Ambush with other AOEs rather than Lotus Fan. Ambush + Whirlwind, Ambush + Soul Tether (ultimate), or Ambush + Shrouded Daggers will all do much more damage overall.

To be fair, NB isn't the optimal AOE class in this game. We're MUCH better suited at single-target focus.

Having said that, there are a few choices for AOE but they all depend on your weapons & stat of choice. Most of our class aoe abilities don't come until higher up in the skill lines.

Look into some of these abilities:

1. Assassination Line
   1. Double Take (Blur morph) - very helpful when starting your pull
   2. Focused Attacks (Haste morph)
2. Shadow Line
   1. Veil of Blades or Bolstering Darkness (Shadow Ultimate) - your morph choice depends on how well you're surviving.
   2. Refreshing Path (Path of Darkness morph)
3. Siphoning Line
   1. Soul Siphon or Soul Tether (Soul Shred morphs) - I actually prefer one of these for my ulti during solo PvE... see below for why.
   2. Siphoning Attacks (Siphoning Strikes morph)
   3. Sap Essence (Drain Power morph)
4. Dual Wield Line
   1. Steel Tornado (Whirlwind Morph) - I prefer this morph and using Siphoning Attacks. Range is much nicer and you don't need the stamina regen with Siphoning.
   2. Shrouded Daggers (Hidden Blade morph) - I honestly prefer Flying Blade but I PvP more than PvE these days.
5. Bow Line
   1. Scorched Earth (Volley morph) - weak damage overall but a nice dot to throw down if you're lacking some of these other abilities
   2. Bombard or Acid Spray (Arrow Spray morphs) - definitely a good one for when you failed to open from stealth

I didn't mention Destro staff abilities because you sound like you're going stamina... but if you're magicka, Destro staff is the obvious choice for your AOE love.

For stamina builds, I'd recommend checking out Jeckll's guide here...

And a couple of miscellaneous notes:
I'd avoid Lotus Fan. I'd still use Ambush with the specific intention of following it up with something that will benefit greatly from your next attack.

For example, using ambush right before Soul Tether will (a)stun everything you hit and (b)can cause upwards of 30% damage to all of the mobs you hit.

For a Bow / DW user, a good rotation & pull could look like:
(Siphoning Strikes on)
Cast Double Take - 20sec duration is plenty of time
Cast Focused Attacks
Refreshing Path
Run in firing a Bombard or Acid Spray or lay a Scorched Earth on the ground
Switch to DW bar as you get close
Sap Essence x1 to get the damage buff
Ambush
Whirlwind / Steel Tornado x2 or x3 at most
Ambush
Soul Siphon
Whirlwind / Steel Tornado as finisher


I've done this myself for fun with plenty of success, but bear in mind that this is a very loose representation of a very generalized prioritization.


With a magicka-based build (without using Destro staff), you can do pretty much the same... except it looks more like this:
(Siphoning Strikes on)
Cast Double Take - 20sec duration is plenty of time
Refreshing Path
Funnel Health on one target as you move in
Ambush
Sap Essence until Ulti is ready
Drop Ulti

Refresh Funnel Health / Refreshing Path / Double Take as (IF) necessary.
Repeat Sap Essence / Ulti drop in-between.

Using Sap Essence with Veil of Blades while you have Refreshing Path and Double Take on, you can actually solo 10-15 mobs without trouble. Granted, they don't die fast.. and you'll never top any DPS meters, but you won't die either. That is, of course, assuming you're all light armor and have something like a warlock set or some freebie magicka pots flowing.