Question for you guys though: I haven't found SAB and SYN to be very relevant in XIII-2 so far and debuffing and buffing is the most interesting aspect of RPG's for me. Am I doing things wrong or are they just useless/not needed?
SYN is less useful overall, sadly. Even though three of the major buffs - Vigilance, Shell, and Protect - are learnable by both main characters and are pretty essential for taking on certain postgame bosses or just trying to take on certain powerful foes early... there is no longer a Haste spell at all, and Bravery, Faith, and the En____/Bar___ spells only appear on monsters, and it's kind of a pain to get them all on one (unless you're using Sazh, who gets most of them, I think). It still helps, but the role overall doesn't pack nearly the punch it did previously.
SAB is still good, but it's hardly mandatory. If anything it's better now - enemies have a set tolerance, and that means it takes a certain number of casts to rack up the 'points' on the effect to trigger it [obviously, more SABs/higher rank SABs speed up this process]. So, you can learn and predict how much of a spell it takes to 'land' the ailment in this one, no unnecessary randomness! Plus, all of the useful SAB spells are on the heroes - the monster-only SAB spells are all the disablers, which as usual either don't work or simply aren't necessary on things. There's really only one time in the game that they're really all that mandatory, however, being a boss fight or two related to postgame-only content; otherwise, they're just there to speed things up with smart use.
Honestly, XIII-2 is generally easier - the main game seems to expect you to do 0 sidequesting, up until the final chapter at which point the game takes off the gloves (suffice to say that it can almost be like the final area of XIII again, unless you've done a lot of side stuff). There's exceptions in the postgame content (boss hunts, paradox ending bosses, Raspatil, and the DLC fights) and even then while the postgame content is fun, it shouldn't be
too threatening.
...Actualy, speaking of which, if you do decide to throw extra money at the game, the DLC fights are probably the best fights in the two entires (if not some of the best in the entirity of FF or RPGs in general, really). Lightning & Amodar can probably be tackled around chapter 5, and the rest progress onwards steadily from there until they are dwarfing almost anything else in the game itself quickly - they also all use unique mechanics and tricks and you really have to figure out how to get through their strategies in order to succeed. I was quite impressed; but it's also a heavy investment for them, so it's really up to you.