Magdks got a buff to their sustain, so basically another source the restore their main resource pool. The combustion passive will restore magicka, if you set enemies burning, which happens very often with all the fire damage a magdk has (for stamdks the same counts for poison damage and the poisoned status effect). Also some kind of buff is, that you can wear arcane elfbane jewelry. This makes the set viably for pve and gives dks more time to spam a direct damage abilities in a rotation or more time for heavy attacks for the sustain.