Yes, 100% no doubt that black runner and black ruffle are the same plant, usually if you see one marked black magic, it's black runner too!
Just bad ID or diliberate mislabeling to sell plants! As hard as I've tried, Ive never actually fought s true black magic!
The plant in question looks generally healthy, I looked pretty hard on my tiny screen and don't see much signs of DsMV, it usually starts right on the the rib veins and feathers out into the margins between veins, unlike that pic with the strong yellowing between the rib veins, which seems to start in the margin and work its way toward the rib veins... But I can't be sure at all, I do see a white mark here or there on the leaves... Without seeing it in person, it's impossible to tell if it's infected, truly it's impossible to 100% garuantee the ID of the plant from pictures either, but it certainly looks and sounds like black runner!
Those runners are doing just what I'd expect, with no roots they can't take up water, and since the connection to the mother plant is severed, then those little plantlets have no source for water, so the leaves wither and turn crispy! Even with roots that's not uncommon!
I NEVER root runners in water! It can work, but it can also rot them, I root mine in soil mix or peat moss, they'll still do all those things that worry you, but they rarely rot. My preferred method is to break the runner at the base of the plant, chose an appropriate sized pot, fill it halfway full with soil, wrap the runner around the inside of the pot, several inches away from the wall of the pot, then cover it completely with several more inches of soil. If the terminal plantlet has leaves, I still bury it very deep, but try to leave an leaves sitting just on top of the soil.
It's pretty foolproof but takes a few weeks to settle in, after a few months you should notice numerous small plantlets emerge from where you buried the runner, each knot or node on a runner contains a tiny plant, and is also where fresh roots emerge from.
