I use Fists of Thunder for the gap closer and the 10% movespeed Passive as means to get more uptime for the Vortex - that gap closer and more mobility is the difference between the vortex falling off or not, a lot of the time.
Small chance, I guess, is because your base crit chance is low. I've noticed the skill stacking up on each crit I make - and using Crippling Wave as my 2nd autoattack, for example critting two enemies with a cleave will pump the aura to 3 instantly.
Continuous is based on your attack speed as is with many other "tick" based spells.
I also use the Dodge Mantra to not have to back out of a fight since you wan't to be there, letting the Vortex work it's magic for as long as you can. I also use Serenity (absorb all damage for 3 seconds) and Blinding Light as means to keep me out of harms way while steadily grinding down waves of foes with cleaving and the Vortex.
Skills that state "% weapon damage" will deal the elemental damage from a weapon. Skills that state "% weapon damage as (element)" will not. So the weapon's fire damage would come through with Spectral Blade, but not with Magic Missile or Ray of Frost.
If the skill deals fire damage, either "naturally" or from a weapon effect, it should activate Conflagration.
Some sources here, here, here.
Best Answer
I'm not sure where you got the 80k number from. Dominance reads:
Each stack will absorb 2477 damage. Since you can have 10 stacks at maximum, your shield will absorb 24,770 damage if you are at maximum stacks. Each time you kill an enemy, it will refresh the full stacked amount of the shield. If you have 6 stacks, for example, and kill an enemy, the stack counter will go to 7, and the shield will refresh to 7 * 2477 or 17339 capacity.
Note that each stack will also extend the length of the shield by 0.5 seconds, so at maximum stacks, the shield will last for 8 seconds on top of shielding for 24,770 damage.