The quick breakdown on specialist wizard is:
Ench: unbelievably good, but a lot of players are going to find it a little dull. Excellent for solo pve, good use in any group pvp. Gives up Illu, but you can work around the lack of imp invis, which is the spell you miss most. Probably the strongest wizard option.
Div: Pretty good, you'll get a lot of use out of the TS signature spell, and the buffed TS. +7 premo is sometimes quite nice. Like ench specialist, it gives up illu, which as mentioned above you can deal with.
Necro: Clunky, and it's a shame imo that its just summon buffs rather than buffs to the death/debuff options in the school, so you're locking yourself in pretty hard to playing in a place where summoning undead doesn't get you crucified. That aside, it's not actually bad.
Illu focus: Ench is one of the easier schools to skip outright. Unless you're relying on it for targeting will saves (and you've got other schools that let you do this if you need it), or doing dominated critter memes, there's not really anything in ench you actually need. in exchange, you get an invis duration buff, and probably more importantly, your invis is going to be 20% more effective against enemies with blindfight (every player that makes attack rolls basically). Moving from 50% conceal to 55% conceal takes you from a 25% conceal miss rate vs targets with blindfight to 30.25% (0.55 x 0.55 = 0.3025).
The rest are flawed, very problematic schools because of what you give up. Generalist is also fairly underwhelming, because you could have been one of the specialist schools. Put another way, wizard has 3 good specializations one specialization that's playable and fine, generalist, and 3 schools I'd avoid.