I probably played more 13 than you, regardless if you liked/disliked the game. Mostly because I enjoyed the combat that much. Anyway, I've plunked 15 hours into 13-2 now and here are things I've noticed:
Combat with "trash mobs" is now less about staggering and more about weakness.Once you learn how a specific pack works, fighting them again should only take a matter of seconds (which makes me understand why the rating system works the way it does now). It mostly boils down into a few categories: packs you AOE down, packs you use elemental weaknesses on, packs you want to be com/com/com or rav/rav/rav for, and occasionally you'll want to stagger some things. This is also taken a step further by many mobs having very low stagger points.
The key thing here is most of the non essential fights thus far into the game are fast. If you didn't like how a lot of the normal fights in 13 (especially about midway through the game) could be lengthy this is a huge change of pace. Personally I appreciate it, especially because it feels very rewarding getting that 5 star ranking when it is much harder to get now on normal foes.
In addition as a last note, each paradigm can be set to focus strictly on AOE attacks, single target attacks, or "normal". The addition of AOE specifically changed one of my biggest gripes about FF13 where there were times your AI partners should clearly be using blitz/aga spells but they simply would not.
There is actual pacing to the gameplay.Probably my biggest problem with FF13 was how it was alot of walking forward killing dudes, cutscene, spend 30 seconds in the menu following the straight line of the crystarium, walking forward killing dudes, cutscene, spend 30 seconds in the menu following the straight line of the crystarium, walking.... Ok you get my point. Occasionally you'd save/shop/upgrade but 80% of FF13 was what I just said. Was this a problem with the game? Personally I think so, but I can defiantly understand the appeal in a generation of games that are exactly like that (Uncharted I'm looking at you!).
Now, how has this been changed in 13-2? Well: menu porn is back! "Menu porn" is that a word? Probably not but it's how I describe this. It really hit me last night after I cleared an area (capturing about 8 monsters along the way) then entered the menu and spent about 10 minutes in there. The new Crystarium while still fast to progress actually requires you to stop and think about what you're doing. Large nodes give a stat bonus to the class you use on it while small nodes give only levels. It requires you to plan your approach accordingly and take a look at upcoming abilities and decide where you want to spend your points.
Anyway, the monster stuff is really where it gets serious. Most abilities (passive or skills) can be passed over between monsters by "infusing" them. This completely consumes 1 monster while powering the other up. It's an oddly intricate system I was not expecting in this game that lets you customize your third party member to some scary degrees. For example I currently have a Commando Chocobo who has poison/physical/fire resist and all of that came from consuming other monsters. Basically what I am getting at is that you can spend alot of time in menus examining monster abilities and then figuring out the easiest way to get an ability you want onto your favorite monster. It's a very RPG-y thing that personally I love and most RPGs of this generation have gotten rid of similar systems in the name of "streamlining". I can't wait to see what kind of ridiculous monsters I come up with by the end of the game.
In addition to this, Square has mixed up how areas flow a bit. Some locales have you starting in town-like areas and then venturing out into the wilds to kill enemies, quest, etc. Others drop you directly into the action and eventually you will make it to a safe haven to chat with NPCs, move the story along, and just in general take a break from constant fighting. There is also more variety to what is going on in each zone. At one point I was in a dark area trying to keep pace with a moving spotlight because once I was out of it a Behemoth clearly more powerful than my level at that point would try to start combat with you (I tried fighting it twice but got my ass handed to me both times) and then at one point I was on the back of one of those giant mossy turtle dudes throwing a clearly upset moogle through the air to capture treasure.
This is probably the most important of any changes I've noticed so far, it constantly keeps the game fresh and I don't feel taking breaks to do other stuff. I've played my entire 15 hours so far in two settings. That never happened in FF13.
5 stars actually matter.I thought about putting this inside the trash combat change, but I feel like it's something that is important enough for its own talk. Something a lot of people didn't realize about the original 13 (and how could they when the game didn't tell you outright?) was that a 5 star ranking meant an extra chance at loot and higher chance at rare loot. This trend continues in 13-2, but it's something you should care about more. Your monster allies do not gain normal experience like the main characters, instead their crystariums are upgraded via items that are sold at shops/dropped from enemies. Early on you can simply buy these to max out the first tier of levels, but where I am in the game the shopkeep does not sell the items I need to keep upgrading stats (these items are split into tiers, my monsters are on the third tier and currently the vendor only sells the first tier items).
Now, how does 5 star ratings factor into this? Well most of the enemies in the game drop these items but only 1 or 2 at a time. Getting a 5 star rating simply means getting these things faster. Almost to the point where it probably unbalances the game. I say that as I currently have a Ravager penguin man who has 400 more magic than Serah (who I'm using as a mage) and triple her HP. He is a freaking beast who can build up the stagger meter and AOE down trash like a champion.