Just make sure you get the Atomic Bonds expansion! The base game is pretty broken and is a 'meh' game at best without it.
With the expansion it's not perfect, but has still become one of my favorites.

Yeah definitely get the Atomic Bonds expansion. The competitive basegame is ridiculously broken. For example there are quests that send your all over the map. But the silly thing is if a quests needs to be "picked up" in one location and "turned in" in another then once it is picked up ANY player can just snipe the rewards if they're close to the destination. Also many exploration options are hillariously random. This makes the competitive version little more than a crapshoot. It's frankly mindboggling how anyone actually greenlit that design.

In coop all that is still the case but instead of being frustrated when another player gets an extremely lucky pull in the exploration, you cheer each other on. Sniping different quest stages between multiple players becomes a cool strategy instead of a braindead design choice. Most of these anoyances fall away and you can revel in the setting of the game.

None that I can remember.
Him escaping via the ocean shouldn't end up being terribly difficult because everyone can tell that's where he is, how many ocean spaces he went through, and cannot backtrack. Usually you can narrow his location down to a few ports.
Mina Harker's power is absolutely critical to use whenever possible. Once you've narrowed position down to a region the game should feel much more winnable because all 4 hunters can spread out and close in.

The bigger issue we usually have with that game is the combat doesn't feel super great and bogs the game down.

Honestly, if you like the hidden movement aspect of the game, I think Specter Ops is the easier/more accessible game to play. It's not that far off from FoD, but it's not as heavy.