Virginia has raised a practical challenge of the inability of experts unable to pass on their expertise.
I think that since expertise consists of (to a large extent) tacit knowledge unfettered by rules and guidelines, this could be one of the main reasons why experts find it difficult to pass on their expertise. OTOH, people at a level below make better trainers, coaches and mentors. They are able to articulate the process they follow. Helping such people to become trainers and coaches would beneficial.

One of the ways to embed support in the work environment itself would be to have managers become coaches. This role change is probably one of the crucial needs of this century.

As Harold has mentioned and I have seen from my experience too, separating T&D from OD and KM creates a barrier to the development of a learning organization. It is no longer a linear world where each department can perform their job in isolation and still expect to remain effective or add value. Everything is hitched to everything else, so to speak.