It's deeper this time around. You have Devil May Cry 3 style movement of dodges and blocks to avoid enemies, different types of weapons with different combos, 2 demons usable at the same time, and most importantly full control over your demons like a turn baseed game. Oh and you have the ability to pull your demons next to you and make them invisible/invincible by holding L2. This means for the defensive side of playing when a boss throws out an attack you can hold L2 and then just concentrate on dodging DMC style with Raidou. Then on the attack you can just do it turn-based style with assigning commands (you can set a command to repeat infinitely as well). You hit the enemy weakness which stuns them and then you slash them and green MP balls come out and refill your MP. Repeat for battles.
2) It's still easy. I mean if you are terrible at gaming it could be hard, but if you're smart enough to use the right elements against the right weaknesses and hold L2 and dodge attacks, you're good for the whole game. Levels mean next to nothing, which is actually a huge plus because it means you can skip random battles (with a lower encounter item) and blow through areas whenever you don't feel like fighting. The fights are ALWAYS fun, which is important to note. The battle system is really enjoyable and boss fights are neat like action game bosses. BUT it is very easy and non-stressful outside a couple of bosses, so the hardcore players will still grief about it.