Is it still necessary to have the images directory in the same directory as the iso for HD installs now,
Yes.
or has this been fixed so that the iso alone is all that is needed?
It won't be fixed.
If the images directory is still required, does this apply to nfs, http or any other kinds of install??
It applies to any kind of ISO install. For non-ISO installs, there are some implicit assumptions made about the location of an install.img relative to the location of the tree, but these are all tweakable with the repo= and stage2= parameters.
- Chris