I believe they're completely gone and not just invisible.
To test this, you can run around with a miracle like Force, Heal, or WoG equipped and watch to see if you get the boost icon (easier to see if you don't have your talisman equipped and the miracle is greyed-out in the HUD). There used to be lots of resonance rings in the Burg PvP spot when it worked. If you stand there now and watch "Force" in your HUD for a while, it seems you won't ever see the boost indication pop up. The boost indication itself still works, but not the resonance rings, so no indication means they're truly not there.
Testing miracle resonance rings with a partner can be tricky, though! I tried to do some testing and couldn't really figure it out. I wanted to know the exact mechanics (if there's a level range, which miracles exactly are capable of spawning the rings, what kind of a delay it has)... but what resulted was inconsistent and difficult to decipher. It felt like sometimes it worked, sometimes it didn't. I had some more ideas for maybe improving my testing, but I can't do that now. :p