But honestly, that's just an old problem. Spellcasters in 3.5 are so good that they make everything else worse by comparison. I kind of just need to accept that and move on. If I imagine that 3.5 is actually a game like Ars Magica or Mage: the Ascension, where everyone is intended to play a magic user, then Complete Arcane is a pretty great supplement. It gives your mages a whole bunch of new stuff to do, most of which is pretty cool.
But while I'm nitpicking differences between Complete Arcane and Tome and Blood, I should point out one really egregious one - the head of the Arcane Order has had his name shortened from "Japheth Arcane" to just "Japheth." New players will have no idea why it's called "The Arcane Order" now.
Okay, joking aside, if I'm not going to complain about the imbalance between casters and non-casters, I'm not sure I have much of a thesis for this post. Just a bunch of disconnected observations.
I really liked the new full classes. The warmage was a little weak, relative to the wizard, thanks to their slower spell progression and limited spell list (mostly just blasting spells, really). On the other hand, this is exactly what I want a spellcasting class to look like. Their magic is centered around a strong theme and they do it well. Blast away, guys, wizards are a joke.
The warlock was another good one. My only issue with them was a minor flavor issue - they are said to get their magic from being descended from fiends, and this steps on the toes of the sorcerer. The later refinement of wizards = study, sorcerers = inborn talent, warlocks = otherworldly pacts is actually a pretty good breakdown. The only change I'd make is to tightly curate the subclasses spell lists based on scholastic tradition/magical heritage/the nature of the patron. And while we're wishlisting here, get rid of clerics and druids and instead roll them into this rubric - if your religion is big on studying a canon and your prayers are actually a kind of hermetic theurgy, you're a wizard, if you're transformed into an inhuman celestial servant, you're a sorcerer, and if you've got an intimate personal relationship with your deity, you're a warlock. In the real world, every magical tradition is also a religious tradition. No reason that should be any different in D&D.
Finally, the wu jen. Decent class, questionable flavor. The tricky thing here is that I actually think their arbitrary "follow this taboo or lose access to your spells" mechanic is a good idea as a general limitation on spellcasters. . . but other spellcasters are just as strong, and don't have that limitation, so what purpose is it serving here? Also, "Wu Jen are the spellcasters of the far east."
And really, what can I say about that except that even leaving aside the orientalist subtext, it doesn't even make sense in the context of the game. The far east of what exactly? Where are the wu jen coming from that's to the east of the game's setting? I guess, if your world is spherical (not actually all that safe an assumption in the fantasy genre), then everything is to the east of somewhere. But even to the extent that you want to say that corebook D&D is fantasy Europe and the wu jen come from fantasy China, there's no actual guarantee that these two areas are going to have the same geographical relationship to each other as their inspirations did in the real world.
Though this does remind me of an idea I had for a fantasy setting where fantasy Rome and fantasy China had a very close physical proximity but were separated by a difficult to traverse physical barrier, like maybe China is in transalpine Gaul or Rome is right on the other side of the Gobi Desert. The idea would be that you could play the main mass of each empire totally straight but have the border region be a polyglot blend of the tropes - a location where Gladiators and Monks could quite reasonably interact with each other.
That only tenuously has anything to do with the wu jen class, however. Except that it exemplifies one of my biggest frustrations with D&D historically - it's fantasy, you can do literally anything, so why does it keep doing the same basic thing over and over again?
Anyway, if I apply that standard to Complete Arcane as a whole, it does . . . okay. Warlocks are certainly a mythological well they've been reluctant to go to in the past. And while it doesn't do anything radical with the genre, it offers some suggestions about how you can mix things up - like using breakable ceramic tiles instead of potions or encoding spells inside architecture instead of spellbooks. D&D has released more daring magic supplements, but this one left me with very few complaints (aside from all the bullshit nitpicking I did in this post, of course).
Ukss Contribution: The Spiteful Imp, a magic shield that will "twitter in evil mirth whenever it deflects an opponent's weapon." Absolutely inspired, I love it.