[3.12] Marks & Curse on Hit

Technical question on the curse changes in 3.12 with the separation of hexes and marks. The patch notes are pretty clear that marks can effect only a single target.
Now i wonder how this works with specifically unique items which apply a mark-type curse on the enemy (e.g. Oskarm, applying lvl 10 Assassin's Mark on hit):
1. As marks only effect a single target, i assume that for each hit of multiple targets, the mark is applied to the last target the skill actually hits?
2. If so, does it effect all other targets at all, mean: what is the order of execution within a hit of multiple targets (e.g. Apply mark -> Calculate hit/damage -> repeat for next target)?
3. If the mark is applied to the last enemy only AFTER hit got resolved, all unique items applying mark-typed curses are essentially de-valued. If so, what are the plans to re-value them?

I wonder this same question too

came here for answers. oscarms will apply vuln but I cant see it applying any marks to anything ever. I also cant get any marks to work at all w/ hextouch. is there a place to find the hard facts on how these work?

Corruptions were changed to trigger on rare/unique. I thought all uniques were the same, never bothered checking though.