Question about new hex reworks and interactions

1) Does impending doom work with new support gems and how? I mean, will hex with impending doom and hex bloom spread hex from first target to second with impending doom on it?
2) What would happen, if i reduce hex duration to negative with ID? Nothing at all? Or curse will not apply, but ID will blow up? If it blows up, will it get benefits form curse?

bump

New supports:

Added a new Intelligence Support Gem - Cursed Ground: Supported skills create cursed ground. Enemies on the cursed ground from a supported skill are cursed with that hex.

Added a new Intelligence Support Gem - Hex Bloom: Hexes from Supported Skills are transferred to all enemies within a certain distance when Hexed Enemy dies.

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We know Impending Doom does not support Triggered or Aura hexes - which is why nobody tested a Blasphemy + Curse + Impending Doom set before.
However, Cursed Ground turns a curse into a Ground Effect. The only other thing we had before, somehow, was Impending Doom Doomsday, but in that set Hexes could not expire as long the enemy stayed in the Hex Area, and when the Area expired, a curse with full Doom applied, meaning max damage from an Impending Doom - and a different playstyle.

1a) Considering Impending Doom triggers when a curse ends, is replaced by another curse (a different one) or just expire, I think Impending Doom will trigger the moment an enemy leaves a cursed ground, since Cursed Ground =/= Trigger or Aura effect. Maybe when we will have lv20 gems, a new tooltip will bar this interaction out.

1b) In order to trigger Impending Doom, the enemy must lose said curse first. So, supposedly you have a max curse limit of 1, the order will be:

a) Enemy is cursed
b) Curse expires/is replaced
c) Impending Doom triggers, dealing damage as if the enemy was still under said curse
d) Profane Bloom would proliferate nothing since the enemy is dead without a curse on

2) You can't reduce a curse duration to negative (Reduced and Less still works in percentages, not in integers), but you can work your way in making it reach almost 0 duration (Anomalous quality may help). ID will trigger as expected when a curse end. Do remember that ID has a cooldown of 0.15, so you may want to look at that kind of duration on your ID-supported curse

My idea was to reduce duration of curses to ~0.15sec(maybe its good to match with cd of impending doom for better dps, dunno). It is possible with alt quality ID, less duration support, less\reduced duration nodes on tree and warped timepiece, maybe add swift affliction and place ID into chest with quality to support gems(or atziri disfavour lol). So if you apply a curse with impending doom to a group of monsters, it could kill like everything on the screen, because curse will spread from one guy to another without any limits, exploding ID each time it spreads. And also because of how big area of effect of hexbloom is.

I think you can reduce it to negative if you get 101 reduced skill effect duration. At least PoB tells that you can

Also, it could work with cursed ground. If hexes from cursed ground have infinite duration, each time you cast a new ground, since you can have only one, old one expires and removes all applied hexes from enemies, so impending doom can trigger. If it works. And i really hope it is. At least ggg didnt say that it doesnt

Just now noticed we have the 20/20 gems. Alright.

I've checked a bit Asphyxia's Wrath, a quiver that has the same "transfer" mechanic from Hexbloom. Turns out that "transferred" curses will not refresh their duration when the new target is chosen - which also explains why I've not found any Asphyxia ID build around - even in the unlikely case I got this wrong and an enemy killed with ID with 1 curse would still retain said curse on death, it would transfer a curse whose duration is expired (or right out canceled by leaving a cursed ground OR a new/stronger curse overrides), which won't happen.

For the curse duration, you should take into account your cast speed too - optimal would be either having Spell Echo and a duration little enough to be expired by the time you do your first curse repetition but not less than the 0.15 cooldown. I'd expect you would be able to roughly trigger ID 4-5 times per second, rather than the expected 6,67

Indeed Cursed Ground + Hexbloom seems to work - or at the very least GGG did not publish a new Hexbloom gem. This won't mean there won't be a ninja nerf or some other "unannounced change so little we thought it won't matter enough to highlight" shenanigan, but tentatively yes - as you suggested re-casting Ground would end the enemy's curse, even if for a fraction of second, therefore triggering impending doom (this is different from re-applying the same curse on an enemy). If it won't work, I'd rather blame a server tick rather than a bad mechanic combination

I will tinker a bit with PoE now that I have your input, since I'd like to see the damage difference between your less-than-0.15-duration version and a Vixen's 3-curse Pathfinder that I had in mind as a leaguestarter. Vixen would raise the CD from 0.15 to 0.25, therefore roughly 3 ID/sec, but will compensate with 3 curses (1 extra curse from Vixen, 1 placed on the enemy and the 1 selfcast expired). I'd also expect a Vixen to be more on budget, but I'll focus on the damage alone for now.

Yeah, i've tested asphyxia. You are right, it doesnt refresh duration. And even if you kill hexed enemy with something else, transfered hexes doesnt have ID and don't explode after duration ends, which is sad.
Ill try crit hexblast then, since it can apply shock and freeze, i think stacking some ailment effect can be interesting.