Yeah, one thing about this game is that the rules are wiiide open and the constant theme through them is "provide the best story". So, you as a Keeper have all the options to make the best fight scene: Two people fighting? Think wrestling ring or epic movie fight scene and use Fighting Maneuver or just a straight punch-up Fighting Brawl for damage. Tentacle wrapped around an Investigator? Fighting Maneuver likely won't cut it, what could you do? Strength roll to open the coil and slip out. Long claws and multiple stabbing legs a la Shelob? Use DEX to frantically dance around between them.
Visualise the story and tell it. Easier said then done I know. I little more than a year in and I'm still trying to get it down.
The important thing is: Do what you think is right to tell the story, let the players drive it. How do they want to fight the monster (given it's attach types)?
