Unpopular opinion (it seems), but I actually love the multiple dicerolls in dialogue.
1) It stops me from simply reloading a save to try again. Maybe other players have more willpower to resist savescumming (I salute you), but willpower is my dump stat in real life. If I realize that with one more point, I could've have passed that persuasion roll, and I quicksaved two minutes ago . . . I reload and try again. But if it's several rolls that are tricky, and I only fail at the third, then I'll live with the consequences instead of risking wasting time. Letting
stay dead was the first time I didn't time travel to save a semi-sympathetic NPC.
That's not a problem everyone has, and the developers should not annoy their players with fake checks for your low willpower's sake.
2) Multiple rolls emphasize that an NPC is extremely unwilling to change their mind--it gives the conversation a different tone, and makes the back and forth feel more like an actual discussion than a simple stat-check. It's more interesting!
A high DC would do the same thing. A back-and-forth discussion is not "Intimidation: Success!" ..but not really, do it again, "Intimidation: Success!" ...but not really, do it again, "Intimidation: Success!" ...but not really, do it again,"Intimidation: Success!" ...okay, FINE.
A back-and-forth discussion could have multiple different skill checks which affect the ultimate DC of the final check. That would be even more interesting than "do the same thing again three more times".
3) It makes me feel like a badass when I
do succeed at several tricky rolls (like with opening
the book on Thay Necromancy and learning speak with the dead
).
Great, but the chance for success is 1% for some of these difficult checks because they're stacked, so few people will see them.
