The comment by one of the prostrikers that was deleted in the middle of page 598 was "I don’t think healers need this redundancy. I think it’s fine they might get kicked if their bad gameplay prevents progress." This precisely what SE is trying to guard against. Also most MSQ encounters are designed so the party can recover if the tank dies but the healer is alive through a combination of fastcast rez and using a lot of mitigation CDs. SE is trying to put redundancy to a healer with increased agency to tank and DPS, which is what the pro-strikers are decrying.
Your remaining linchpin rebuttal point of "just do trusts" is ironic because pro-strikers in this thread also decry that Yoshi-P and forum users allegedly respond to pro-strikers' complaints with "just do ultimate." You are responding to my point with the "just do X" logic. In any event, SE is not going to assume every single player is either going to "get good" or just sit in trusts. I believe another person in this thread pointed out that SE seems to also be motivated by trying to police and remove negative player interaction as much as possible. Whether rightly or wrongly, this is the overarching policy decision they made. And the attitude like one of your pro-strikers with a moderated comment of "I don’t think healers need this redundancy. I think it’s fine they might get kicked if their bad gameplay prevents progress" is why SE cares about redundancy and not making healers a single point of failure where there is a possibility of interaction with other players (ex: Duty Finder).
My suggestion of giving an raise item to everyone usable in instances like a pheonix down is a potential alternative that would reduce the likelihood of negative player interaction. SE then may feel comfortable adding more complexity and increasing "stakes" for healers because there is more redundancy built in that inherently will also mitigate negative player reaction. More redundancy means less likelihood of one player/one role risking the entire DF group's progression and then being blamed.