/pre-submit edit: holy sh...oelaces, I've written another novel. Short summary for the tl/dr crowd and those with little time:
"EVERY game has necromancers who can animate the dead but don't have to (if they have necros at all). A necromancer who needs his undead for almost everything would be new and interesting, and not yet_another_diablo2_necro."
----------------------begin novel-size rant/brainstorm/hopefully source of inspiration------------
Well, while I don't have a lot to add anymore about the historical background, I'd like to add my 2 cent about a necromancer's secondary abilities...
I'm a bit bored by them, actually.
I start a game as necromancer, and find that animating corpses is a "can", not a "must". This bothers me a bit since imho animating corpses is the defining characteristic of a necromancer, but as long as I can still choose to play a pet-focused necromancer I won't complain.
But then there's the next stage of this... necromancer classes/guilds in some games can animate undead servants to help them... but are better off NOT doing this because their "secondary" abilities are actually stronger. Necromancers who don't bring their pets to parties because they aren't worth the loss of experience for the group or because they'd just fall over and die on the first mob big enough to warrant bringing a party. Necromancers who don't put skill points (or training, or whatever) into their pets because blood magic, curses, spirit chants or whatever the game in question has benefits the party more and thus is a more efficient use of mana/spell points/whatnot. Basically they take the weaker half of the spells a mage and abjurer would get, rename them to have a loose connection to necromancy, and give that class a pet with a "you can use it for soloing and RP but don't bother bringing it if you team up with other people" power level. That's just wrong.
Now I don't want to come across as all negative, so here's what _I_ would love to see:
A necromancer class/guild that actually focuses on the animated undead. Maybe uses ONLY them.
Can this work? Maybe it requires some tweaks, depending on what game you want to implement it in.
The starting levels are the first hurdle. "but a new player at level 1 won't have any animated undead, what is HE supposed to do then?" - Take this dagger/staff/scythe (depending on what feeling you want to give your necromancer), kill that goblin over there ->, animate it. go from there. You'll soon notice that it's better to let others do the dirty work.
Balancing... a VERY hard task with any class, even more so for necromancers. You don't want the pets to be useless, but because the player doesn't put himself into as much risk sending the undead into the fray as he would if he'd fight himself, the pet can't be as powerful as a fighter. I'm not sure if this CAN be done without either side complaining at all. You can give the pet *almost* as much power as a fighter if you implement harsh penalties for dying pets, but you don't want the necromancer to become unplayable when his pet dies, either.
And last (for now) but not least, would a necromancer even be useful in a party? Maybe your game prevents too many people from joining into melee, or maybe small rooms in your game do this. Maybe melee damage isn't enough to be worth a slot in a party unless it comes with a meat-shield attached. Maybe a caster-type NEEDS some utility (paralyze, status effects, direct damage to ANY target rather than only those in melee range...) to be useful for a party... That's where a "real" pets-only necromancer class becomes a nice dream only, never to be implemented in that game. However, you can get pretty close if you tie all that utility to abilities of the pets - possibly abilities that require the necromancer to persuade the undead to perform them. Think of this as spells or skills with the pet as material component.
You want your necromancer to be able to paralyze an opponent? "cast undead tackle at <petname> target <monster>" (or some variation of that), the pet will try to hold said monster. This kind of trick could be VERY interesting if your necromancer class allows for pets with widely varying attributes, since you'd want to have a big, strong undead for stuff like this tackle but would rather go with a faster skeleton-type undead for better attack rating and damage if you wanted more damage. Or you could put your effort into creating a more mystical undead (ghost? grim reaper?) who wouldn't do much damage in melee but would give the most damage output when using "soul strike" or something like that (causing the undead to use its connection to <negative plane of your choice, or whatever your game uses to explain undead> to <drain away the life force of the living opponent, absorb the negative energy of the undead opponent, or taint the magical energy animating the construct opponent - these could actually be three different spells/abilities>.
This would again be a necromancer who uses damage blasts, (de)buffs and/or status effects, but the necromancer would have to actually behave like a necromancer and animate the dead. And for RP/flavor/immersion it's just SO much nicer to have the frankenstein's monster grab and squeeze the bad guy than create some nondescript magical tentacle or soulcage or whatever, or to have the festering giant zombie stand between the squishy members of your party and the enemies' archers than to create <yet another glowing shield-like effect thingie>.