That wouldn’t really do much unless they also made Arcane Orbit quite a bit stronger. And I don’t think you actually don’t want it to simply give the Arcane Orbit rune, you’d want it to do what it does now but benefit from the Arcane Orb multipliers.
Right now, you can have both Arcane Orbit and the Moonlight Ward orbs active, so (up to) 8 total orbs. So if the Moonlight Ward orbs benefited from all the Arcane Orb multipliers, Moonlight Ward would effectively double your DPS (+5% elemental since it rolls up to 25 instead of 20). If it benefited from the multipliers, you could consider it roughly a 2x multiplier.
But remember, it’s competing with Squirt’s Amulet (or Endless Walk). At a 2x multiplier, at best it’s really only a wash with Squirt’s or Endless Walk, both of which are 2x multipliers.
If it gives the rune instead, then you can only have a max of 4 orbits out, not 8 as you can right now with Moonlight Ward + Arcane Orbit. And you’d have to run a different rune on your bar. The obvious choice is probably Obliteration (would make more sense for a hybrid melee build since it explodes on first contact, not a fixed distance like with Frozen Orb). But that just seems weird to me.
A better option might be to still have it give the extra orbs, but make the power something like “you can have 2 sets of Arcane Orbits active at once and Arcane Orbit does 80-100% additional damage” (and you should be able to have an orb from each set explode at the same time, not only one at a time).
You don’t want to make it a generic Arcane Orb multiplier, because Orbit damage is too low compared to some other runes (cough Frozen Orb). So making it a generic multiplier would leave Orbit still behind. Making it an Orbit-specific item would be better. Double Orbits + double damage would make Moonlight Ward a 4x multiplier to Arcane Orbit. It would immediately outcompete any other amulet options for Arcane Orbit builds, and might make Arcane Orbit viable again. And if the 100% multiplier part is too weak (it probably is), you could tweak that to get the power of Arcane Orbit where it needs to be.
Another nice benefit of Moonlight Ward is it’s very easy to roll an Arcane / CHC / CHD / socket since it has Arcane and CHC as guaranteed rolls and crucially it doesn’t have a guaranteed int roll. So you have two random primary affix rolls, and you need one of them to roll as either a socket or CHD to make a trifecta. It’s much easier to roll a good Moonlight Ward vs. a Squirt’s or Traveller’s Pledge.
I always keep a good one stashed in case it’s ever useful for something someday. Although I guess I’ll probably need a new one when that day comes.
