Game says I'm 37% in. I keep getting stuck on some of the tougher sea missions. I was first stuck at the mission where you take on the Man O' War so had to go back and collect some dough to upgrade my hull, now I keep getting killed on the very next mission when you're trying to board the slaver ship. I really suck at the sailing aspect of this game.
The assassins are more or less in the backdrop of the storyline so far. I'm not sure I mind this at all. It makes sense that they wouldn't be very strong in this era. Plus, it would be pretty cheesy if a guy like Edward who is motivated by greed just heard about the creed and went "oh yeah I am sooo an assassin now".