I'm against the HOF's death (she took the DA, and she was a Alistair romance). And if they killed the HOF offscreen, image the load of pure crap they'd get about it
It's fairly certain that the HoF won't be killed offscreen.
Killed ONscreen, on the other hand...
What you want is for people's choices not to matter a crap. Like Hawke. All of what Hawke did meant so little in DAI, I just started to not care about Hawke.
I know that people got sick to death by the endless comparisons to Witcher 3, but here's an article about the Witcher 3 that's relevant to this discussion:
Role-playing games, including my own, have a lot of what are sometimes called false choices. These are points when you make a decision or express your opinion, but your choices don't have a concrete effect on gameplay.
I don't believe false choices don't make a difference. In fact, they are hugely important. By asking the player to mentally engage and form an opinion about what is happening in the game, you are directly shaping the player's experience.
Remember, video games are just tools we use to affect our brains. The only important thing about a game is how our brain perceives it. Any choice, even a false choice, affects our perception of the game. All choices matter, even if they don't affect your stats.
The Dark Ritual is important because it helps defining your Warden's personality.
The thing is, for all their vaunted expertise, Bioware sucks at moral dilemmas: either they'll give the player third options copout (Don't know who to choose between the Werewolves or Elves? Fear not you can save both! Don't know whether to sacrifice Isolde or Connor? No problem: you can save both of them!) or make the benevolent choice much more beneficial (to abandon the CIty Elves or save them and accrue much needed evidences against Loghain? To ignore the multiple pleas for aid and fetch quests or gain sweet loot and XPs by doing the people's bidding?).
As a result, it doesn't matter if your character is selfish or selfless: since the most beneficiary way to play is virtually always to make the benevolent choices, any Warden endowed with a modicum of foresight and political acumen will for the most part make the same decision as a goody-two-shoes Warden -even if they happen to be a sadistic brute who toyed with Caladrius like a cat with a mouse- because that's where they interest lies.
On the other hand, the Dark Ritual's only immediate gain is whether your Warden remain on good term with Morrigan or not. Every other potential consequences is several years down the line: this is a choice that barely affects your party stats (at most you loose one character out of a roster of nine), but which tells a lot about your protagonist's personality and priorities and whether they're putting their duties to the Grey Wardens first or not.
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We don't know if they found the cure for the Calling. I suspect they didn't. So at some point, all things being equal, the HoF goes tromping into the Deep Roads.
Although that would make for an interesting (and welcome) twist (the great invincible hero failing and coming back home empty handed is a conclusion seldom made in fantasy stories), that won't happen, because sending the HoF to their calling is pretty much giving them an offscreen death.