Invisibility to the hearing sense group would still cover the ring. No one has argued invisibility to sight would stop a sound, you using that as an example in the first place is a complete non sequitur from the topic.
You state:
"Invisibility doesn't make the SFX of your powers stop being obvious so the SFX of "ring is obvious because it shoots tinymagical shields" remains obvious. Again, Darkness construct."
Well, per the rules the SFX of a mundane weapon like a sword is that it is an Obvious Focus of a Power. You are arbitrarily granting some SFX a bonus over others, regardless of your attempts to justify it.
Also, nowhere in the rules does it state that the Images Power produces light (unless you are specifically building a light power). Claiming the "light escapes Invisibility" is a nonsense arguement based on your idea of certain SFX and had nothing to do with the rules of the game or how Powers are actually described as working.
EDIT: Also, claiming someone with a Distinctive Feature can't be turned Invisible is just crazy to me. I don't even know how to approach that. By your own standard someone with the Distinctive Feature: "12 foot Lizardman", Not Concealable (no Ninja Turtles trench coat is going to hide this guy) could not be turned Invisible.