Ordinator, it revamps the perk trees and will greatly enhance the experience of playing a mage or a mage-hybrid.
Problem with magic in the vanilla game and Destruction in particular is that it doesn't scale well with increased difficulty. Weapons and armour you can smith to godlike stats, best you can do with destruction is +50% (75% w/Dragonborn masks) damage and 300 armour from ebonyflesh w/perks.
Conjuration scales since damage out and damage recieved for summons and reanimated mobs is the same regardless of difficulty setting, it only affects the player.
Illusion is also god-tier as long as you have magicka and don't miss your target in difficult situations, or just cheese it with zero cost enchanted gear.
Restoration is the most useful school, and the most boring, every type of character can benefit from it. Ward spells in the vanilla game are underpowered, higher ranks cost too much to sustain, even with the ward absorb perk which returns 25% of the hostile spell magicka cost, again we need to rely heavily on enchanting to bring the magicka cost down to managable levels. Another thing is that a lesser ward can negate dragon shouts, that's right, even the more powerful shouts are useless against it. Turn undead spells are useful for a character that has Restoration as a major skill, you need to keep your skill and spells up to date for them to affect draugr as you level, they will stagger undead regardless so it's not completly useless when faced with Deathlords, Circle of Protection can be dual casted to deal with them.
Alteration, there are a couple of instances where it's obvious that the designers made Telekinesis a useful spell to have, flesh spells can benefit every type of character as well. The winner of this school is Paralyze, high magicka cost, but enchanting solves that problem.
To sum up, necromancer would be one of the weaker subclasses, frost spells don't work on dwemer automatons, alot of enemies are resistant to frost, and the perk that paralyzes targets with low health will cause reanimation spells to bug out, the mob will just stand there as if the paralyze is still in effect. Reanimation spells apart from Dead Thrall don't last long and can be tricky to cast in combat, easy to miss, in addition they will turn to dust. The redeeming factor is that they level Conjuration fast especially if you're using the unofficial patch, no more casting soul trap on a corpse or bound sword when enemies are nearby exploit.
Ordinator takes care of all of the above problems for the most part, a necromancer is is very much viable with this mod, it even offers disease spells in restoration if you want to skip frost magic or combine the two. And it's not just great for mages, every type of character benefit from this mod, currently I'm playing a 2h heavy armour warrior with some restoration, no points spent in magicka and just the atronach stone and resto perks.
Edit: I should add that there are perks in this mod that supports a playstyle that involves wielding a sword and staff if you want to be like Gandalf, there's a perk in enchanting that's called "You shall not pass" - "[FONT="]Simultaneously (within 1 second) using an enchanted staff in your left hand and striking with an enchanted weapon in your right hand releases a flash of light that staggers enemies and deals damage based on your Enchanting skill level."[/FONT]
