Why?

[Thrice Dead Cat]

When a source just becomes available, that's a bit different. The DM should expect change requests in that sort of situation. But if there hasn't been some sort of a change, this is what the DM might hear:

I gave it as a possibility. Even now, a lot of people don't have certain splats for one reason or another. I've seen a few threads recently where someone suggests something from an Eberron book for an Eberron game and the response is "I/my table doesn't have that."

"Hey, would you mind designing a whole extra side quest that will put the spotlight solely on me and possibly interfere with an existing time-sensitive quest, so that I can make a change that I should have thought of when I was leveling up? Oh, and by the way this will make my character a lot more powerful than it is now, and since I've done it everybody else at the table will want a chance to switch out their least useful choice."

If the DM says that, I'd suggest getting a new DM.

More seriously, just talk with the DM on it. Explain your situation in that case and go from there. Maybe it will turn to the point where everyone gets their own sidequest, but, as both a player and a DM, I love that idea. As a player, I like things that directly involve my character and can also enjoy it when it is someone else's time to shine. As a DM, I want to make sure that everyone has their own plot threads so that they each feel more involved in both the world and world building.

It's obviously not always going to be like that, and many DMs will be receptive to changes that fit the fluff particularly well. But it's not always going to be as simple as, just go and retrain. This is one of the reasons why I'm a big advocate of the DM working with the players (especially the less-experienced ones) and offering suggestions when leveling.This sort of thing doesn't crop up as often, and is usually handled smoother when it does.

Eh, certainly. Generally, I feel that if a DM has qualms with a splat "because it is OP" is a bit too close minded for me. Are there splat books with some high end OP-fu in them? Yeah, those are core! Seriously, though, it's not the book that's the problem there: it's this one (or two) thing inside it, but I digress.

In general, it should not hurt to at least ask your DM for a possible retraining sidequest and working with him from there. If he says "no," ask why and talk about it to see why and go from there. Depending, you may get him to agree, but, if not, well, I hope he has a damned good reason for it.

There's something that's been bugging me about asking for build advice lately. I'll post a thread asking for some sort of advice, and after a few token questions from others, everyone basically ignores it. I may attempt a makeshift build and post it, thereby bumping the thread and providing a framework for critique, but it seems to just get pummelled to the second page, which nobody ever reads.

It seems like if you're not talking about how class X is overpowered or how class Y sucks, you're not going to get any help for a class that's just "average."

My trend is to not jump into a thread if I see a bunch of posts with relevant advice, simply because I'm of the mind to read through all or most of all of the posts to get a bearing of what has already been said and what yet hasn't. Other times, I simply just drop a link to the most relevant handbook and be down with it, since my advice will just be a parrot of what was found there-in.

It's not about off-topicness. They'll ask a few questions related to my question, apparently needing clarification, but after I provide said clarification my original request is apparently forgotten about because some other thread has pushed it down.

Don't be afraid to PM a mod and ask to either bump the thread for a few days or to start a new thread with some of the compiled info and go from there.