Glyfair said:
I didn't find it so, until the end of the 3.5 cycle. Psionics was always sort of an "optional core" and would often appear in small doses in various books. Campaign settings core book were "core" for their setting. Other than that, you didn't see references between books (except swift and immediate actions which had their rules reprinted in every book).
The first book (I think) that really assumed you had other books that weren't the PHB, DMG, or MM was PHB2, with its inclusion of Complete classes like the Warlock, Favored Soul, and Scout...as well as the Marshal, from Miniatures Handbook (which I think was 3.0...).
Before that, you had the occasional psionics reference, and in the occasional adventure you'd have one creature/NPC that could be adjusted if you didn't have the books (psion became wizard, say). Hrm, though Races of Stone had stuff for the Scout before Complete Adventurer came out...
I'm perfectly fine with them assuming you have other books, because I do, and many other people do. For those who aren't completists/collectors, the DDI will likely be very helpful in this regard, since you could likely reference stuff on an as needed basis, so that adventure you got that includes monsters and classes from the 3s isn't useless.
In 4E I have a feeling that the PHB/MM/DMG series will be the books referenced in other books, and everything else will mostly be contained within that book, with the D&D Insider used for expanding the roles of popular things.
This seems like a reasonable supposition, especially with DDI. They can use that so if it becomes apparent that class X is somehow incredibly well-received (say, like warlock was), they can support it until they can shove it into a PHBn.
Brad
