Here are my summarized thoughts now that I've completed all four campaigns and had a bit of time to reflect.
I think the campaign I consistently enjoyed the most was Chris. Leon's was also great, but fell short on a lot of sections. I found Chapter 3 to be a so-so drag in comparison to the rest of his campaign, and I really did not like his final boss battle(s). Chris felt fun throughout and I enjoyed the way his scenarios were constructed, probably as I am a fan of the bioterrorism concept and do not feel his action-slant is out of place because I like that narrative.
Jake's felt pointless and would have probably helped the game if it was left out entirely or Jake/Sherry were relegated to cut-scenes. You could remove his entire campaign without losing anything in regards to either gameplay or narrative, and outside of a few particular segments, his campaign was completely forgettable. I never properly used his melee and when I did, I felt it was too weird to control. If this was the campaign to reel in new players, I think they dropped the ball into an abyss.
The story was so-so. Suga should really stop writing for the series, and it's unfortunate that Murata was pulled to write for Dragon's Dogma. However, the character dialogue is some of the best in the series and the background details in the files are very nice, especially those relating to past games. However, I felt certain characters were underused. I really liked Simmons, but disliked
. The clone angle was completely unnecessary and fell flat in execution.
Ada's campaign was neato. No real complaints about it. Ada herself could have used a bit more background.
Overall, I'd give it a 7. There are things I really like and things I really hate. I was right in assuming it was going to be a very polarizing game. It's difficult to quantify the game as a whole as it is so wildly inconsistent in parts and has an immense amount of actual content, which don't go well together. The sections I did enjoy were fantastic, while the ones I didn't were a drag. I try to take both into account and not let one or the other dictate my entire experience. I was right in assuming it was going to be a very polarizing game. Also, QTEs suck balls. I have had more fun with BH6 Mercenaries than any other Mercenaries beforehand.