I'd like to build on this.I used to use Silks of the Sun on my mDK- but then someone pointed out that Burning Spellweave is much, much better. After giving it a try, I have to admit... the up time and damage of BSW is much better than SotS.
Plus, BSW would increase all of your damage from ALL your magicka abilities (even more beneficial since you're a Magblade)... not just fire based attacks.