One of:
1.) Account-wide research progression
2.) Account-wide coalescing visions
3.) Account-wide rank 1 cloak without the questlines/scenarios
4.) Account-wide cloak ranks
It’s insanely tedious and dull to spam the life out of visions/quests to upgrade the cloak. Please do SOMETHING.
They can choose not to, and they will.
But that would disturb Blizzard’s time-played metric. 
Either that or they’ll do it 2 weeks before prepatch where it won’t matter but they can say they did something.
Maybe the upgrades after rank 15 onwards being account wide?
That way you only have to keep it up on one character, but still have the ‘challenge’ of bringing it up to 15.
It won’t happen its the only content for the patch so it had last for 12 months just another way of extending the game with no content, along with the boring same wqs day in day out and people think things will change in SL? sorry but Blizzard and Ion sit around a table all day not making new content but finding ways to make it s-t-r-e-t-c-h and last longer for the LACK OF CONTENT.
We couldn’t even get a brand new zone in the final patch of an expansion, that’s the saddest part
So you want to funnel all to your best character and the rest get it for free.
IIRC - Visions are only here until SL comes out.
So no, no account wide anything as it pertains to visions.
Do them, or don’t.
Everything with these new expansions starts from square 1 anyway. Whatever you gain in these visions will be moot when SL lands.
IMHO, time will be better spent on leveling ALTS to explore the 4 new covenants.
The only thing would be the questline, but now it’s possible to do some skipping there, so it’s shorter than it was.
Actual progression within the Visions should be character-specific, like any other gear progression. Early runs are extremely fast and easy. After that, it’s still reasonably engaging solo content. Even if you’ve done it on a main character, there are different strategies for other classes and specs.
Eventually it can reward good gear.