Ok, so I think I'm in the home stretch. I just got the electric tether which, like Jay has espoused, is amazing. I have four side missions showing up on my map which I would imagine will be the last ones and then probably the final story mission.
I have all the shards. I was at 303/305 when I purchased the shard locator upgrade although I don't think I needed it. The last two shards were on pier type areas that I hadn't really checked yet so I'm pretty sure I would've found them on my own.
I only need one more dead drop, and no, it's not the one back in the swamp where you start the game. I checked a guide and figured out about that one. I'm glad I checked because I probably would've been beating my head against the wall looking for it because I would've never thought to travel back there, especially considering it doesn't even look like you can get back there on the map. Now I just need to figure out where the last one is? Do they appear based on where you are in the game or are they just always hovering in the same areas no matter what. Because I'm pretty sure I've been everywhere on both islands.
I guess when I start my Evil play through I'm going to have to play on Hard so I can platinum this bitch.