you are right, there are a few solutions to fix that
3) Allow all rings above level x to have the same value at +12 as previous items at +16... maybe even a little higher. (This is the better idea.. cause it gives an incentive to get newer gear, but doesn't hurt those that have done the previous system.
Then do the change. It would be better for the game as a whole to go back to +12 as max.
That is good. Just look at level 82 earrings +16 and lvl 80 earrings +16.
Level 80 - +4860 HP
Level 82 - +5436 HP
New gear does scale differently with plussing. If it could be just that much better for gear over 80, it would even out the turf.