Vials of mist in 30+ fractals
The only time I have ever gotten a Vial in 30+ Fractals would be during the Jade Maw Fractal, almost always from the adds summoned by the Jade Maw itself. Otherwise, I normally get level-appropriate Mist Essence.
If that is where you’re getting those Vials, then it might be a bug related to the trash in that particular Fractal.
I am Fleeting Flash, in-game dungeon cosplayer of Reddit Refugees [RR] .
I’d like to point out that, by my experience, level of mist essence can also be capped by your personal level. So if you’re playing f38 with personal level of 1->9 range you’ll get only vials. (Noticed this when I leveled up my 2x in 3x and 4x dailies.)
edit
Also, my 66 toon gets shards in his 4x and 3x dailies, so I wouldn’t put my bet on your rollover theory OP.
Outsource rng → profit.
(edited by Articluna.4509)
Enemies that are summoned by other enemies drop vials regardless of the level. So things such as the things the maw spawns, the dredge that pop up from the dredge suit, and the barracudas that spawn from the kraits are things that will give you vials instead of globs/shards.