The Arcanum Ring was always going to run into the problem that the components are just a hodgepodge of abilities. Eldritch at least followed a pattern to some sort of coherent conclusion with the individual tokens.
Arcanum Shirt might make sense, though, looking back at my posts about Arcanum, I pointed out that it didn't need to be +everything and could have been like Dungeonbane where you choose one thing. "Fortunately", Shirt only had four things to worry about and one of those things is irrelevant to most classes.
What I would do to control for power is have Ring choose from the component effects. This will, of course, never happen because it's not grossly overpowered when the reality is that it was obvious that Arcanum would just end up being better than Eldritch. (Almost like that was pointed out years ago on the forums, too.)
For instance:
Choose two at start:
+2 AC
+5 HP
+2 Saves
-2 Melee Damage
+1 INT/WIS/CHA
1st Ring would, of course, in my alternate reality, only give +1 INT/WIS/CHA.
Then, I would have set bonus be actually comparable to Eldritch as well as ditch the +1 level as +1 level is absurdly easy to find in the game already ... if could figure out what sort of identity Arcanum is even supposed to have. Not like Eldritch set had much of a coherent identity, and the set bonus for it is not terribly coherent, but Arcanum sounds magical in a very magical way where AC, saves, HP don't come across as all that magical in a very magical way.
If Arcanum is supposed to have a defensive identity, which is what is happening at the moment, then, sure, can add to AC, saves, HP.
Given my expectations that Arcanum would blow Eldritch out of the water, I'm not really surprised that every Arcanum token has been overpowered and set bonus will be significantly better than Eldritch set bonus.
A problem with Arcanum is that there really isn't much precedent to base power level off of. URs, relics, legendaries, rares, uncommons, commons have lots and lots of history (at this point for the higher end stuff). Arcanum has Eldritch, but Eldritch is a small number of tokens where the power level is wildly variable.
I might run a rare over SRoEC. Always will run Skull in power builds, but it's really just providing +1 damage and pass a Will save in most of my builds. Four Winds is essentially +6 damage, which is hard for anything to compete with. Dungeonbane is what I consider the best value high end token in the game for its versatility and power and low price. RoSP is interesting powerwise, where I rarely feel bad for using the segments in my second, third, fourth, and fifth builds for runs as I didn't bother getting multiple Rods. Yet, as slotless, it's by definition BiS.
I have a hard time imagining any Arcanum being as bad as SRoEC or Skull are. So, will get individually high power token with set bonus that's more than just +1 damage for every additional piece.