How does one determine which deps are required rather than wanted
A very good question, to which I unfortunately don't have a very good answer, but I'll voice my opinion.
When I go to install a program and notice that a long list of dependencies are listed, I make a note of it, then install the desired program package by itself. Next, launch the program from a terminal prompt. If no errors, fine. If there is an error about a missing piece, go ahead and install that package. It may be necessary to do some research to figure out which package contains a certain lib or executable. Searching for it in gslapt often helps.
This unusual dependency chain usually occurs when you install a piece of the Gnome desktop. Due to the integration of the programs in this desktop environment, you may end up with a full Gnome installation to support the application you select in gslapt.