Non-CP PVP, including BGs, is very different to CP PVP. Due to the fact that you don't have CP there to boost your stats and make up for where your build lacks, you will have to explicitly build for things if you want them. You also have to make choices over what stats you build for, and what you neglect, because trying to build for one stat leaves you short on other stats.
This is likely why you have low sustain (assuming by regen you mean magicka and stamina), as non-CP builds typically have to manually incorporate sustain into their build. Most players choose to run a sustain set as one of their 5-piece sets, but some might choose to run a recovery mundus, a few recovery or cost reduction glyphs, or just change up their playstyle to heavy attack more often.
The way I look at non-CP is like a triangle, where damage, survival and sustain are on each corner. Trying to build for one leaves you lacking in the other two, but building for all three leaves you with all three being relatively weak. Most builds are balanced around two of them, with playstyle picking up the slack for the third.
A magDK build I had focused more on survival and sustain, which meant I could stand toe-to-toe with somebody a bit easier than normal, but I mostly relied on lucky Skoria procs to close kills, since my damage was lacking.
Yep, a solid piece of advice I heard a while ago that stuck with me, is that it's easier to make a light armour build tankier than it is to make a heavy armour build hit harder. Light can run sets like Fortified Brass, Pariah, Riposte, Bloodspawn, or use a couple protective traits on jewelry to make up for the lack of resistance, while still keeping the extra sustain and penetration light offers.
As for your builds, there's a couple problems and alternatives I can see,
- Ele Drain is on the wrong bar, you can't use it with sword and board, so it'll have to move up to your front bar. I'd maybe swap around Ele Drain and Engulfing, and simply switch to back when you debuff with Engulfing.
- I'd maybe try Entropy instead of Molten Armaments. It does require a target, so you won't be able to pre-buff with it, but it's much cheaper, applies a minor dot, a minor hot, can heal when you light/heavy attack, and it gives a little extra mag and mag recovery on your back bar.
- I'd give the sword and board ultimate a try over Meteor. When I tried destro/snb, the sword and board ultimate was fantastic for survival, taking a ton of pressure off when you really need it.
- I wouldn't use the Thief as your mundus, as crit really isn't that strong in PVP. Can help a little with healing, but doesn't do much for damage, since everybody and their mum runs impen for crit resist. Apprentice would be best for straight damage and healing, Mage would be a little worse off for both but would be better on sustain, and Atronach for straight sustain.
- Your tri-stat enchants are on the wrong pieces, unfortunately. Big pieces, ie helmet, chest, legs, give the most resources for enchants, so you want your tri-stat enchants on your big pieces.
Aside from that, they look good. Maybe a bit of enchant tweaking, to get your sustain at a comfortable level (with practice, magDK can easily sustain with 1200-1300 recovery, though I prefer higher myself). When I was playing (taking a bit of a break at the moment), I was trying out a light armour build using Bright Throat and Silks of the Sun with Bloodspawn and 3 protective jewelry. High recovery, like 1700 in no-CP, or just under 2k in CP, respectable damage, decent max mag, sat just under the resistance cap with Bloodspawn up (spell resist was just over, phys was about 3k under), and could leap often due to the ultigen from Bloodspawn. Would definitely recommend giving it a go.
I’m no DK expert, but I’d think blood spawn monster would be better than Skoria. I’d think a proc aoe wouldn’t be as good as more mitigation plus more leaps.
Maybe as a DK you can get away without blood spawn, IDK. Thing is expect maybe 10k pen from opponents, 15k with ele drain. From another class’ perspective without wings you’re still a little squishy.
Leap is one of the best ultimates in BGs, blood spawn is good for offense and defense. Without enough mitigation you’ll also always be playing on your back foot and can’t be aggressive.
As a rule of thumb, the more aggressive you are the tankier you need to be, and vice versa. A typical new pvper mistake is to try and spec too much into damage thinking it’ll help them get kills. In reality they just die a lot and always have to play defensively so end up doing less damage.