I get your point, that every encounter should feel meaningful, but I don't think monster hunting should have this kind of focus in Original Sin. The Witcher is about a monster hunter and CD Project Red did the best they could to make this a fun part of the game (compared to the first two games). One of the main themes of The Witcher series is: "Who are the real monsters? Those who are, or those who do?". In Original Sin 2 the theme is how will your past shape your future, or something similar. I think the quests that emphasize this theme should have a very different structure.
If you look at Original Sin 1, I actually think they've already done a lot of what you are proposing, just not with monsters. MINOR SPOILER: You are two source hunters who come to a quite town, that has reasonally had a lot of trouble, with crazy orcs, undeads and a murder. When you start to dig deeper you realize that it all has one source - a sourcer (pun inteded). The resembles a lot of the mystique behind the monster hunting in the witcher intentions and so forth. You go in thinking it's just side-quest, but it's actually the main narrative and the theme that is introduced.
What they didn't do in Original Sin was having you research the best way to take down monsters and finding the enemies weak spots. I loved this in The Witcher, but it also goes a little bit against the philosophy of Original Sin as this game is about doing everything in you own way, finding your own solutions and being creative with the systems.
I think you have some good points, but I would personally prefer Original Sin 2 to be even more like Original Sin than more like The Witcher.
