Seems to me after a few hours of testing that the level drops on rings in vota and desolate sands are a little too high and that your more likely to get a manald heal.
Sewers of caldeum, ruined cistern dalghur oasis all seem to be around the right level, problem with the 1st two is that there is such a lack of champ packs. I haven't managed to get a ring to drop yet in the forgotten ruins to check level.
I'm sure it is possible to get one in vota, but it doesn't seem like the most effective way to go about it.
I'm going to try for a few hours on getting 5 stacks then running Adria quest in sewers and clearing up to the desolate sands.
I'm running 375% mf after nv.