magDK is not the best, but it's really fun but can be hard to play, give it a chance and you will love it more then any other class

i am using
5heavy 1light 1stam(and level up your Undaunted skill tree for passives)
2 blood spawn(because we need ultimate, maybe you can try skoria,not tried it by myself)
5 kagrenacs
3 willpower
1h+shield torugs pact, you can run it on both bars or use resto staff on second

abilities:

for 1v1 i am running
Burning embers
Flame lash
Deep Breath
Dragon fire scale
Fossilize (use it right after you use meteor,with good timing,target can't cc break and block in time and get's full dmg from meteor)
U: meteor

secondbar
Proximity detonation
Entropy for spell dmg buff
free slot, sometimes i use Talons there, sometimes Harness Magicka against sorcerers, or fiery grip
Dragon blood or Blessing of restoration,depends if you are running 2x 1h+shield or resto staff
Volatile Armor
U: Dawnbreaker of Smithing because it really hurts vampires and i love this ultimate,you should try it

if you are playing in group against groups, put Talons on first bar instead of burning embers and Igneous Shield on second bar

i don't think SaB + destro staff is good idea, also Invasion is not good as it used to be before Tamriel unlimited, we dont have that much stamina and you need stamina for blocking etc, also gap closers are bugged and not working most of the time in pvp

if you want, you can run destro + resto with light armor to make it really work, but DK really need a shield

put volatile and other buffs on second bar, try my bar, after few hours of playing you will realise what abilities you need and that you dont have time to switch to another bar, like me i really prefer to have reflect on main bar,also with fosilize so i can stun in time before my burst, DK needs good timing since we don't have that much dmg, our only chance is mostly meteor, so as i said, buff up, deal some dmg, meteor and stun right after and there we go, target is dead.

Bar 1 sword and shield
Deep Breath
Shielded charge
Burning embers
Degeneration
Flame lash
U- shooting star

Bar 2 resto staff
Volatile armor
Healing ward
Dragonfire scale
Burning talons
Proxy det
U- devouring swarm

5 piece julianos
5 piece vicious death
2 piece Valkyn skoria.

BEAST set up.