If you want to play a Necromancer there is only one path open to you. Evil Undead summoner.
Necromancy is a whole school of magic, and yet of the three paths that you can take to specialise, (Spell Foci, Specialist Wizard class, and the Prestige Class) the only path that isn't purely about your summons is the Prestige class that turns you half undead.
Yes. If you want to be a Necromancy mage without Undead summons, you are better with Pale Master levels than any other option because Pale Master boosts necromancy spells that dont involve summons. (Specialists get all of 2 non summon spells that get boosted and one of those is HIGHLY situational.)
Necromancy is the school of magics related to life, death, soul and body. Yet all a necromancy specialist can hope for is slightly increased DCs on (admitedly numerous) negative energy/drain spells that are worthless in PvP because everyone has Neg Energy Prot and restorations out the whazoo. Defiler Clerics at least get to convert some of the damage to Entropy, but this is not a solution as this is essentially turning the spells into Hybrid Necro/Evocation spells.
So as things stand, if you want to play a Good or Neutral aligned Necromancer your options are either Palemaster (Avoid going down the undead summoning path by becoming half undead instead!) or Defiler (focus on necromancy by making your spells less necromancy'y.)
It is hard to think of a solution, but I do think the first step is to give Wizard Necromancy Specialists bonuses to some of the spells that aren't undead related. If a wizard wants to be a super undead summoner they already have Palemaster as a path. Give them something else instead.
Vampiric style healing perhaps? A portion of all Negative Energy damage from Necromancy school spells is granted as healing to the mage? Maybe even as a small amount of temp HP to all nearby allies?
Half damage is Negative Energy half is Positive? Reaching back to the days when Necromancy was the school of both, and the healing spells were in the school too.
A portion of the damage can bypass Neg Energy protection or even harm undead?
Give them an option. A Necromancer with Undead Summons under their control work as normal. A Necromancer without instead benefits from one of the above. (Undead dominated by Control undead could fall either side of the restriction depending on balance)
Either way SOMETHING needs to be done. No school of magic is inherently good or evil, even if many of the spells in Necromancy are, the school itself isn't, but 99.999999999% of characters that will ever be played that focus on it will all be evil.