If you could describe what you feel is wrong, it may be a good place to start. You're proposing that there is some problem, but there is no comment on what the problem is. Just a 6 minute video with no commentary.

I see a mag dk. mismatched sets, moderate cp. Training dummy dps check. There is some room to improve I would think, but you could say that of any dps parse.

Full sets will help your dps overall. The 5 piece bonuses tend to be of large benefit with good rotations. I'd work on getting that 5 pc burning spellweave set finished off. That should be a nice dps bump. I'm not a huge fan of spider cultist, but it is an easy set to farm so you can try to get 5 pieces of that as well or maybe go with crafted julianos if you have it available to you. Silks of the sun is another decent choice and not too bad to get a hold of in guild traders for reasonable prices.

I didn't catch the food you're using, but Witchmother's Potent Brew is usually a solid choice that won't break the bank. It will help with sustain. You'll see a good dps increase from gold weapons (which it appears you have). I didn't catch the trait, but infused is very, very good right now, especially combined with an absorb magicka enchant on your front bar. More damage and more sustain. Back bar infused with weapon damage enchant will keep that uptime near 100% combined with wall of elements on that bar. There are loads of other smaller things to work on such as full divines on all your gear, golding them out and solidifying a good simple rotation, then refining that into something a bit more advanced. Something as easy as applying 3 - 4 dots then weaving lava whip is a good place to start if you can sustain it without too many heavy attacks.

After another look, I'd say to try and get a Burning Spellweave neck as a first priority. It will finish off that set and also get you a bit more magic overall. I'll agree that swapping spider cultist for Julianos is probably the easiest and more affordable option that will get you the greatest gains overall. A second Burning Spellweave ring before you craft up the Julianos set will put you in a very good gear position.

If you're on PC/NA, hit me up and I'll help you farm out some more spellweave items. If you can't craft the Julianos yourself, I can get that for you too.

@redspecter23

On another look. I HIGHLY recommend you to use a mundus stone buff and a buff food like witch mothers potent brew or just a simple blue health + magicka food on CP 150/160 level and after that to put all points into magicka if you don't need that health based on requirements, playstyle or personal preference (for example some people aim for 15k some for 17k some for 18k..)

Ok for what I see, you want to improve DPS, so here some tips:

1. Use food. (Witchmothers or Blue food max mag+max health)
2. Use a mundus stone. (You can use thief, Lover, Apprentice)
3. Aim to get or transmute your gear to "Divines" trait.
4. Weapons, as of right now, should be infused. Try to get the weapon on the second set, complete (unless youc an complete BSW with inferno staff)BSW in body while you farm the staff.
5. BSW is a great set, Spider Cultist is not.
6. Use potions of spell power with spell crit.
7. If you are on PC use addons to help you use skill on cooldown not spamming them when is not needed.
8. Try to pair BSW with some sets like: Julianos, Mother Sorrow (recommended cause you can farm in zone or buy it), Silks of the sun (recommended cause you can farm in zone or buy it), for pure damage.
9. Spider cultist is a bad set bc it only buffs destruction staff skills, and basically you will use only, on magDK, wall of elements.
10. You can use while you get better to do Vet Maelstrom (for inferno staff), use a Willpower inferno staff.
11. Try to work on a rotation, this is the most importan point, a rotation for magDK roughly could be as follows:

BACK BAR: Light Attack (LA), wall of elements, LA, Eruption, LA, trap (or psjic if you have access), LA, equilibrium (for sustain)/bar swap/
FRONT BAR: LA, Flames of oblivion, LA, engulfing flames, LA, Embers, LA, whip, LA, whip, /bar swap/

Roots are for pvp, pulsar is rarely used.