I've got a few important questions that I don't think were addressed in this thread.
-Does it matter whether you're a vampire first or get the Necromage perk first?
-Furthermore, does Necromage affect everything only after becoming a "Necrovamp"? That is, will the Augmented [Element] perks confer more than a 50% damage increase only if you were a Necromage/vampire before taking the perks?
-Does Necromage affect the Novice-Master perks that reduce spell cost?
-Does it affect Destruction spell damage in general, like making Fireball do an extra 25% damage? Does it affect the Vampire Drain spell?
-Does it just affect the length of time that which one can reanimate corpses, or also the strength of the enemy? That is, can a Necrovamp dualcast Dread Zombie to reanimate a mammoth?
1) it doesn't matter if you get the perk first or after the bonuses, but you need both at the time to get the perks boosted, it doesn't affect previous perks.
2)I'm not entirely sure, I can't test it out as I'm on Xbox. But there is a link I'm sure, my flames spell does more damage than it should (perk taken after being a necrovamp). You will only get the boost from perks if you are a necrovamp at the time of taking them.
3)Not sure about the spell cost perks, I would think it does boost it to 62% reduction.
4)It doesn't affect spell damage in general, on spells such as fireball and thunderbolt. But I think it does do something to the spells cast on you, like fire storm and blizzard. I can take off 1/3 to 1/2 of a draugr deathlords health with fire storm on master, they have 1200 health so I'm doing a lot more than 200.
5)The necrovamp link affects duration of conjuration spells, that will get boosted by 50%. The necromage perk also increases the effective level of those resurrect spells, so I can resurrect deathlords with the dread zombie spell (they don't move though sadly). The necromage perk only boosts spells on undead though, so mammoths won't be affected, other vampires and draugr will.