DK have a passive called Combusion, and it restores 500 magicka or stamina when you apply burning or poisoned respectively. Generally people argue that this is the worst or one of the worst sustain tools in the game. At some point it was, and eventually we got to the state we are currently in, the ability has no cooldown, so whenever you apply either of those status conditions you will regain resources.
The chance to apply any status effect is as follows:
20% on enchantments
10% on abilities
5% on area abilities (first hit)
3% on single target dot ticks
1% on area dot ticks
The passive Elemental Force from the destruction staff tree will double all of these for burning, chilled, and concussion. With the a gold charged trait on our weapon, this increases further by 220%. After everything is considered our chances become:
Edit: math
100% 84% on enchantments
64% 42% on abilities
32% 21% on area abilities (first hit)
19.2% 12.6% on single target dot ticks
6.4% 4.2% on area dot ticks
This increase is quite substantial, even in a single target scenario as seen below. Combustion accounts for a whopping 463 Magicka per second in terms of recovery. I had 99% uptime on the Burning status, and it ticked 255 times. I was only in combat for 237 seconds and so I have to assume Burning was ticking basically every single second. This actually drives our DPS up quite a bit as Burning accounted for 6.3k of my total DPS. I was bash weaving with Crown poisons, so a good comparison would be to liko's MagDK parse
here.
Charged also increases the chances of applying the Poisoned condition, driving up the DPS gained from poison up to 2.8k and the stamina regeneration allows for more bashing. Since the magicka return from this passive was more than substantial I dropped absorb magicka enchantment on backbar and used a Flame enchantment.
My point is basically, consider a Charged trait. With a few changes to your build it should result in greater sustain with little to no DPS loss. Any adds that happen to wander into your area dots will have a substantial chance of getting burned by both Eruption and/or Wall of Fire which only further drives up the returns from Combustion since it procs without a cooldown. I have little doubts that this extends to pvp scenarios as well, although to a lesser degree, so it may not be worth the damage loss.