After xpac there will be 6 ‘Necromancer’ masteries available:
Xpac Necromancer
NCFF Necromancer
D3 Necromancer
Darkest Dawn Necromancer
Grim Quest Spirit
Coronus
I think it’s time they had their own undead mod comp. 
Do you become Uroboruus (spelling) incarnate if you combine all six? 
Could always include Necrotic, it’s not undead/necromancer themed but it has “necro” in the name!
Witch Doctor has some undead stuff as well with Zombie Dogs and Zombie Wall. Maybe the DoH Ritualist? I don’t actually know what kind of skills it has.
According to nexus Ritualist is focused on elemental damage, primarily the dots.
Ritualists (subject to change?) are spellcasters that have harnessed elemental forces, making Fire, Ice, and Lightning do their bidding. Due to their specialization they lack in skills that able to inflict instant damage, but their attunement to the Elements makes up for versatility and the ability to inflict massive Elemental damage-over-time.
Accepting combo names at this time:
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Necromancer + Necromancer = Necromancer
Nah, need names of various undead. Lich, Demi-Lich, Shade, Ghoul, Skeleton, Zombie, Wraith, Ghost, Dracolich, Banshee, Bodak, Geist, Revenant, and so on.
Your tags.txt is going to be nice and simple.
Maybe something more like this:
Necromancer + Necromancer = NecroNecromancer
Necromancer + Necromancer = Necromancermancer
Necromancer + Necromancer = mancerNecromancer
Necromancer + Necromancer = NecromancerNecro
Necromancer + Necromancer = mancerNecro
Necromancer + Necromancer = mancermancerNecro
Necromancer + Necromancer = mancerNecroNecro
Should add different fonts for each class tags, make it more ＡＥＳＴＨＥＴＩＣ