For the most part, Creed's internal logic holds together and creates enjoyable gameplay. At times, though, it falls apart and creates unintuitive situations. Rooftop archers are a deadly nuisance and can take Altier down at range. The counterbalance is that Altier has a limited number of throwing daggers that can kill with one hit. But that, in turn unbalances the main assassination missions so the arbitrary rule is made that throwing daggers cannot be used on primary targets.
Another strange situation occurs in the mission to assassinate William de Montferrat in Jerusalem. At one point he sits astride his horse in front of his stronghold, airing his political dirty laundry to an inferior while surrounded by a crowd of onlookers. Rather than strike him down while he's distracted and relatively unprotected, you must wait till he's retreated back into his well-fortified castle and surrounded himself with dozens of well-armed guards. If we'd had our way, we'd have chosen to strike during the speech with a throwing dagger - escape would have been much easier that way.
There are also strange quirks where pickpocket targets will vanish and reset to their original position while you're stalking them. It breaks the otherwise flawless technical continuity of the world, but may yet be fixed before the game goes gold.