I saw Dissidia and got a headache from just watching it. Granted I was WAY out of the franchise by then so my interest was way low already, but when I want a spin off about fighting...well I want a fighting game and not a mash of pretty lights! In terms of fighter spin-off, I would rather pick up persona 4 arena (and no I don't own it: I'm terrible at fighting games). If anything I could add Dragon Quest heroes - does it count as a fighting game? - but as a "Warrior" game is pretty mediocre.
For world of final fantasy...I dunno, it just feels so uninspired and boring to look at that I just preferred to get a copy of Berseria instead. At least Tales games have fun combat and Berseria had also a pretty amazing plot! And no I have no idea when that game was released: all I'm doing is showing my thought process when it gets to rpgs.
My sister owns Theathrythmn and she said it sucks...and suffice to say I trust her more than anyone else in the world. And final fantasy explorer....I prefer God Eater.
And sure I will take your word about Nier: enjoy the game. I just don't trust its quality. Sorry!