I felt the battle system of XIII-2 was a downgrade and easier then XIII. The enemies themselves were also easier. Like Long Gui and Yomi for instance.
It wasn't really that the battle system was downgraded or made easier in any way. It was the entire game that was made that way. The battle system is as good as identical to XIII. It's just that the enemies are weaker and easier to fight now, compared to XIII where you actually needed Debuffs and Buffs to survive several battles and Med was your main source of healing since Potions only healed 150/300 HP.
XIII the best of the 3 by far. LR tho is easily the worst. But I think those who enjoy it the most are action game fans, who like fast paced reaction time type games. I consider LR a action game with RPG elements.
LR is not worthy enough to be called an action game.