I'm curious about DW on a magic class too, if anything the light and heavy attacks would scale on weapon damage + stamina now, and there's a little bit of both. Of course it would still be a very tiny light attack damage in comparison to staves which are hitting very hard lately, and it can be very annoying to run out of magic on a Nightblade while on the dual wield bar since heavy attacks will only return stamina.

Back on the magblade/stamblade topic. There is one thing bothering me now ever since magic got buffed with Summerset. I usually play Nightblade DPS with cheap looted potions since I'm always throwing gold at other junk. If my Bosmer Stamblade isn't using crafted power potions and poisons, then it's doing less DPS than my Breton magblade using cheap looted blue potions.

Weapon damage is the bread and butter DPS buff for stamblades since there are a lot of weapon damage multipliers in the kit: 12% medium armor, 3% fighters guild + 5% Flawless Dawnbreaker, 20% major brutality + 5% minor brutality. WD adds a bit more base damage than stamina, so stacking WD is the thing to do. It can be buffed a whole lot by major brutality, which comes from crafted potions or less efficient skills.

Magicka on the other hand has a lot of multipliers on a Magblade: 6% Undaunted mettle, 8% siphoning skill line, 2% mages guild + 5% inner light, 20% CPs, 9% Dunmer. It's so close to matching the buff from spell damage that you may as well pile magicka as high as you can. I use the Mage mundus over Apprentice. I'm pretty sure in the absence of minor sorcery from a Templar, magicka is the stronger source for buffing damage, even if major sorcery were active.

My magblade has a very lopsided magicka pool in comparison to spell damage. Crafted spell power potions don't really add much and now, unless I feel like burning through crafted weapon power potions, my stamblade is doing less damage than my magblade.