is it 50% of the game that's spent in shooting mode battling repetitious enemies? I really wish it was just the other side of the game, but I know the publisher forced the shooting section upon the developer. More than 50%, less?
I will use every cannon, every bomb, every bullet, every weapon I have down to my own eye teeth to end you! I swear it! I'm coming for all of you! -Laura Roslin
You can easily spend tens of hours playing it like Shenmue in Twin Peaks land - talking to the townspeople, doing sidequests and driving challenges, collecting trading cards and new weapons, tracking down every one of the bones (don't talk to Kaysen in the diner or he'll steal them), eating lunch at the Sheriff's office to watch the hilarious cutscenes, exploring the weird outlying areas you won't ever have a plot-critical reason to visit, driving around unpaved back roads in search of Agent Honors, playing darts, buying new vehicles, fishing, snooping in people's windows, and the list goes on.
Or you can ignore all of that, and just let Emily, George and Thomas hustle you through the story, which largely consists of visits to Shadow-infested Otherworld dungeons..
In the first case, your experience will be weighted heavily towards "townplay." In the second, it's about 50-50. If you get stronger weapons and the Field Combat suit that's an Amazon DLC preorder bonus, the gunplay should go by a lot faster.