Actually AC:Revelations did aswell.
Yeah there is a lot of content in this game. Kinda hard to keep track at times.
Nah, you didn't need to sign up for Uplay to play multiplayer in Revelations. I know this cause I was playing it not too long ago.
On to combat!
Basically, you have two main weapons, your main-hand weapon (tomahawk, sword, dagger, etc) and your ranged/misc weapon (bow, pistol, snares, rope dart, etc) and you can basically combine the two to form combos and special attacks. You basically attack using Square/X to strike your opponents until you hit that last hit that actually kills the opponent. Any hits prior to that final hit are, apparently, worthless. Once you kill an opponent you can immediately switch to the next target and perform a chain kill.
You can maintain a chain killing as long you are in range of your next target, and you are not interrupted/hit by another enemy attack.
You have an counter stance and a break defenses (guard break button). Near as I can tell, break defenses is mostly worthless. It seems to only work on the weaker enemies and won't work on the tougher targets. Counter stance basically gives you the ability to parry different attacks and strikes. Certain weapons are actually better at parrying than others. There's a "just-frame" input on counter where the action slows down that gives you time to perform a counter-kill, disarm or throw. What you really want to look at is the counter-kills and the number of ways you can make this work.
For most enemies, whenever you make a counter-kill you basically press Square/X and pound the target with an instant-kill technique and then can go on chain-killing. Certain enemies, however, will break your counter-kill techniques (Hessans, the kilt-wearing fellows with the axes). However, there are options on how you perform your counter-kills. For example, if you are facing a tougher enemy target and you do counter their attack just right, instead of using your melee weapon (sword, axe, tomahawk) use your ranged/misc weapon instead (bow, snare, pistol, rope-dart). This will kill all the tougher targets I've encountered so far.
More importantly, whenever you're comboing on an enemy target you can actually mix and match attacks, shifting between your Square/X attacks with your Triangle/Y attacks. You can even do this during chain kills, and whenever you do this 'right' you can actually get some really cinematic kills where you end up killing two or more enemies at once.
There's also a way to bait two enemies into attacking at the same time. When that happens, if you hit the counter button at the right time, you'll go into a lengthy cinematic kill, killing both targets at once. I'm not quite sure of the trigger, but whenever your see the opportunity, take the chance.
Finally, there's a way to kill any target through enemy fire. When you see yellow triangles, it means the enemy is planning to strike you with an unblockable attack. Usually these are fire-lines or a pistol shot. When that happens, target a nearby enemy and press X/A you'll grab the target and use him as cover for enemy fire. Incidentally, you can use this tactic for defeating really difficult enemies.
Finally, since combat is much stronger and 'easier' in this game. There's almost no reason to run and hide from the guards after being discovered. Not only do they now have new AI patterns that pushes them to constantly search even when you're not in sight, blending and in general hiding from them is much more difficult than prior games. I'm not sure how they messed this up, but they did. So if you're stuck having to deal with guards in town, just kill them all. Blending/hiding and running from the guards is pretty weak in this game.
Finally, its possible to kill/assassinate without picking up any notoriety all. In fact, its even easier in this game than prior games. You don't even have to blend to do it.
