Problem is once you die, even once, you lose all your MP and suffer a 25% potency loss or so to your cures. So if you play the MP management game, you've raised the stakes for a healer dying quite a bit. Combine that with lower potency base cures, and either its much harder for healers, or you need to target them less with instakill mechanics. And there are times when even in hard content I see healers who are new or not so good die twice. You can recover from that now, but if its much more triage-y it actually makes it worse.
(1) then you get blamed for not saving people, even when it isn't possible. As it is now, you can save some attacks, but you're not able to carry people who legitimately screw up beyond a point.
(2) You couldn't save anyone but a tank from hashmal. I have pretty fast reflexes, and I couldn't beat the server tic on healers or dps on it. Maybe now that some DPS can hit 45k HP, same as tanks at min ilvl when they did it you can save them, but that's not a good example. And as it is, a lot of healers don't even esuna titan's gaol debuff, slow debuffs, and more erasable mechanics unless it one shots the person.
(3) No, none of those mattered all that much. The problem with procs is that unlike DPS, we really don't get benefit out of randomness in cures. We can't really just use a bigger cure when it procs, and a lot of ogcds that proc might as well just have a strict timer if we hold on to them for specific boss attacks. that's the problem with the whm aoe buff (whose name escapes me)...its proc based, and its really worthless many times since you don't need it. And they tried to make people need it by doing double aoe attacks, which just made it more annoying for sch and ast.
And as it is, proc-based gameplay barely works for WHM. SCH in particular couldn't deal with it much, and AST's rng stuff is the cards.