I saw some comments, and a post, where people were saying maybe, just maybe, some loot might have a higher chance of droping depending on your talents / Spec / whatever, so here is my testemony, for what it’s worth.
As I mentioned, I saw a few comments, and a post claiming this, so I thought 1 is a coincidence, 2 is worth a shot… So I created a new toon, my friend boosted me, and I specd into Werewolf / Tornado… And I got mine like 15m ago, with a perfect roll (first unique of the day…)
I’ve been grinding on my Pulverize druid for 2 weeks now, since level ~60 doing NM above 31 - My main dudu was boosted, and then I took a ride for a while with a friend. 90% of the NM I grinded, was targeted, meaning, I mostly did NM with Cultists or Cannibals. I only saw Tempest Roar drop once, which funny enough, was for the same friend while boosting his druid - also, he was specd into Werewolf / Tornado abilities. Aside from this, I saw like ~10 Vasilys, ~5 Mad Wolf Gee’s, ~5 Insatiable Fury’s, ~4 Great Staff of the Chrones, ~5 Hunter’s Zenith’s, ~3 Waxing Gibbous, and a few more random like the Mothers ring, or the Thorns chest, among others.
I grinded everything, helltides, NM’s, Worldboss’s, Whispers, Obols, I even went as far as to yesterday out of desperation switched to World T3, and grind some Sacred NM just to see if I got it as sacred… I never got the head… I also created another Druid to try this strategy last week, but never gave him skills, didn’t see the head drop but a bunch of other uniques dropped… The day I “switched” - I didn’t really but created another toon and specd into werewolf / tornado, I get the head, on my 51 druid…
I mean, I know rng is rng and all that, but to me, it’s to big of a coincidence. I really believe some loot is more associated with specific specs / talents, which at the end of the day, makes sense. All loot is eleigible to drop, but specific loot has a “higher” chance to drop.
At the end of the day, it is what it is, and these are my “2 cents” about this… Onword to try and kill uber lilith now I guess 
To everyone still grinding, hey, try this strategy, might surprise you and you only lose some gold, or if you have a friend to boost you, do like me, create a new toon, ask for a boost, and you don’t lose anything, just some time. Keep strong fellow Druids!