I don't actually disagree with anything you're saying, but in these particular stories I don't actually think any of those complaints apply.
Data is obviously a special case, if Spock was then Data certainly must be, and
Again, weird for me because I generally agree with you, I just think these two particular stories were really nicely handled.
And as for my point about Before Dishonor and Nemesis, you'd mentioned that it removes emotional impact from death if it's later reversed, and mentioned the shocking and profoundly affecting death of Duffy as your example. Which, again, I agree with. But I didn't feel any emotional impact from Data's death or Janeway's, in their particular works. So I don't think their resurrection is in any way making Nemesis or Before Dishonor worse. Really, BD was a preposterous comic book romp; I don't think anyone was getting to the end with a tear in their eye!
Full Circle does a much better job at making Janeway's death Really Mean Something, but I've got enough faith in Kirsten MF Beyer to believe that all of that character growth won't be reversed just because she's back again. I could analyze that more deeply if you like but I don't think it'd make much sense if you hadn't read the story to see what I'm talking about. (Again not a judgement! Not trying to be snarky! Feel free to skip any book you don't want to read, it just makes it harder to talk about the specifics...)