Alright, my final comments, then I'll probably bow out of the discussion.
I have only one gameplay experience to contribute. A group of my friends ran through a troll related one shot adventure posted on the wotc website, and used the PHBII and the Tome of Magic to create their characters, just to test them out. The shadowcaster was, I believe, level 12. It contributed well to the party in spite of being played by a less than expert player, particularly due to the level 5 wall mystery, and sight obscured (sorry, don't have my book here, don't recall exact names). The wall mystery is very solid, has no save, has a duration, has high damage, and blocks line of sight. Sight obscured is great if the target fails its save. I could easily see their view of it as being different, however, if their target had made its save. Other than that, the shadowcaster waltzed around enjoying his Collar of Umbral Metamorphosis, and did not do a whole ton of stuff. The heroes were the Duskblade and the Monk with Decisive Strike.
Regarding Ehren37's comments: The various builds you suggested are solid, but of course have drawbacks. The Arcane Trickster, for example, requires less than useful feat prerequisites, and lowers your max spell level and your caster level. Yes, it contributes other things, but its not a wash. I had forgotten about Twilight armor. The only thing I can say regarding it is that I think publishing Twilight armor was a mistake on wotc's part. It gives armor to classes that previously did not have much reason to use it. I recognize that normal casters are freed from concentration checks eventually, but using no custom items, that level is approximately level 15 for a caster with a 14 constitution and skill focus concentrate. That's the level the caster can cast a 9th level spell and succeed at casting defensively while rolling a 1. The shadowcaster, at the same cost of one feat, can get Shadow Cast, which, the vast, vast majority of the time, negates the need for concentration checks while casting. This can be obtained at level 2 by use of a bonus feat.
When I review a class, I tend to think its ok if I can make at least one decent character out of it. I think I can do that with the shadowcaster. Its probably a little weaker than a tweaked out wizard, but to be honest, I've always felt that the primary spellcasters were overpowered. Maybe I feel more comfortable with the shadowcaster because I don't see the power of a primary spellcaster as appropriate for the game.
Finally, I don't diagnose the shadowcasters problems the same as everyone else does. Everyone seems to have a problem with the way the shadowcaster's mysteries known translate to mysteries per day, and the total number of mysteries a shadowcaster has per day. Personally, I think this is what makes the shadowcaster unique and interesting. If you took away this mechanic, you'd just have an alternate version of the beguiler. So, I'd like to make a change without altering the path system. What I'd do is, rather than complain about mysteries per day, I'd worry about GOOD mysteries per day. The path system forces you to choose mysteries you may not want if you intend to get past them to better options. For example, to get the very fun mystery Flicker, you need to go through the first level mystery that mimics the Command spell. At level 1, that's ok. But at level 14, being able to cast 3 supernatural Commands per day with a saving throw of 11 + cha is pretty weak. You're probably never going to use them at all.
Here's the change I would make.
"The DC for a mystery is equal to one half the caster level of the mystery user's casting class, plus the caster's charisma bonus, rounded down."
I would then alter Path Focus to no longer give a bonus to mystery DC, merely the bonus to caster level.
Now, apprentice level paths that were previously very, very weak (the one with Flicker, Umbral Mind) and initiate paths that were so so (basically anything that forces a save negates mystery on you) would now grow in power level as your character grows.
This would have the following effects.
First, at low levels, Shadow Hood would actually be a good choice. Right now no one even discusses it because after a few levels it becomes 100% useless. Making it worthwhile increases the shadowcaster's offensive options. It would still be weak, but its a fundamental, so that's ok.
Second, it would encourage taking multiple paths or unusual paths at low levels to pick up attack mysteries. Selecting Umbral Mind is kind of a weak option right now, because Mesmerizing Shade, while ok at low levels, becomes terrible at higher levels. With a scaling DC the ability to Daze a target as a supernatural ability is worthwhile even at very high levels. With the scaling DCs, I could see a player taking Mesmerizing Shade or the mystery that mimics Command purely for their own value, and not merely for a way to get past them to higher level mysteries within their paths. This would increase the combat spells per day available to a mystery user at lower levels, effectively increasing mysteries per day without changing the flavor and mechanics of the class to mimic a wizard.
Finally, at higher levels, the fact that mysteries like Mesmerizing Shade would be a viable combat option would lessen the need to desparately pursue attack mysteries. Taking Dark Reflections would be less mandatory, and players could loosen up and select options like Step into Shadow or Bolster or Dark Air and Water with less guilt at the loss of offensive power. This would encourage a larger variety of builds.
As of right now, when I say the shadowcaster is an ok class, I guess I'm really only referring to two possible builds. One is the one I listed above, and even it is a little slow at low levels, and the other is a touch attack based build. There are whole paths I would never even consider simply because they involve too much dead weight that cannot be dropped at high levels. Scaling DCs would ensure that this would no longer be a problem by making that dead weight useful, and wouldn't meaningfully impact the overall power level of the game, because even a scaled DC Command mystery is still just one round of Command.
And it really fits in well with the whole "Shadow magic is different and superior to normal magic" thing the flavor has in it. And with the way mysteries really aren't spells, they're something different that eventually matches supernatural powers.
Anyways, that's about all I have to say on the subject. Thanks for your time, Mouseferatu. I'll read replies, but probably won't comment much.
