Well its true something probably needs to be done sooner or later ... and its also true many find the nodes an they're somewhat okay with it as things are, however, at the same time others players (*like beginners) would find searching for nodes at the beginning of there journey really frustrating (it all depend on the person naturally).
Adding a few new icons as guidelines at the beginning is great and all, and so far doing so has helped many to understand the game better, and it also look a bit better too. (
[But personally at many points for gathering I can't completely agree with op, adding more and more helper icons it doesn't quite feel right and overdoing it could be bad.]
"We are Gatherers, We Search and Explore, and if we still can't find that material and its location (??,??) then that is okay as well because other people might know better then you do, so look toward them for guidance"; "We are Gatherers and what is a gatherer if they do not search for themselves and peal the dangers of Eorzea without fear" [*as well as looking for the mats is half the fun in it for DoL/Doh I'd say the least.]
So whatever does happen its got to be more Unique and interesting, even more showy then the current glowing ball effects so much so that people take notice right away, and possibly when said class rank-up is high enough the icons would soon disappear giving more challenge, or and reducing the repetitiveness of it all.