I think it’s a case by case basis, personally. I agree with you about Curse of Doom. It’s either a weird, silly ability or it’s designed to be so overwhelmingly powerful that any raid with a warlock would be foolish not to permanently kill a player to make a doomguard. There are ways it could work (example: if they changed the spell so the sacrificed player commanded the doomguard), but not sure it’s really needed.
Other abilities were iconic to their classes. Auras aren’t a great example for paladins, but seals were. A huge part of Paladin gameplay used to be choosing your seal and swapping it around as needed. Different seals were used in different circumstances, and it was fun.
Now, that being said, I don’t know if I want to see all the pruned abilities come back unchanged. Like seal gameplay was fun, but it would be more fun for the choice to not be so binary. “I need to use X when I single target and Y when I AOE” isn’t fun. Using seals that augment my abilities based on what I want to do, however, is fun. I’m looking forward to seeing what Blizzard does.