As a counterpoint, sharing spellbook card lists may not be the best contribution that can be made. The theory that a well tested spellbook encapsulates is the result of experience, thought, debugging, and a play style unique to the builder. Even with the book list, another player will probably not wield it as well so what benefit is gained?
What may be more productive is looking at things in a more granular fashion. Instead of trying to distill the essence of a spellbook into a forum post that doesn't always capture the finer points, I informally suggest a method used in certain competitive games in Asia to improve the overall body of experience without selling yourself out. Study sessions are gatherings where people share specific situations with varied criteria, state their approach, and open the floor to friendly discussion. This can yield a variety of opinions and theories from different perspectives. Think of it as discussing the best way to build individual tools instead of asking someone to explain their whole toolbox, which, in some corners of the world, is considered rude.
Although it is not a direct analog, this is already kicked about in the Strategy and Tactics channel, but might benefit from a more organized approach. For example, propose a specific situation along with any relevant details of the game state (either from a game you played/witnessed or pure speculation), explain how you might manage it, and then start asking how a warlord might crack this nut; or a wizard, or priestess, or beastmaster. Anyone is free to offer their perspective, though if they expect to be taken seriously they should back up that position with an explanation. Both sides of the conversation can benefit from learning how other classes of mages might respond while giving the mage of example some insight into how to best defend their position. Participating helps evolve the game of everyone involved by making more informed choices when building their own books instead of generic netdecking.
I want to point out that in the context of your suggestion for more open sharing of competitive spellbooks, even you are reluctant to share your best.
I'll be posting some more of my *less-used spellbooks* soon.
(emphasis mine)