Finally managed to platinum Tales of Graces F last night (or this morning :P) and I'm thinking it's a 3* one. It's certainly a game that has a lot of grinding, from the Mixer Maxed trophy to the GentleMan one (probably the two biggest ones in the game). There is one missable inn request for the GentleMan trophy, so if you miss it you are probably looking at another playthrough with another 15-20 hours of gameplay (if you rush through NG+). Of course, you are most likely going to need another playthrough, anyways, for the 60 seconds boss trophies. While it's not a terribly difficult platinum, it'll still take somewhere between 100-140 hours for most people, and there is some difficulty in the game despite being able to adjust the in-game difficulty at any point. The difficulty trophies aren't hard, since you only have to fight the final boss to get them.
They definitely could've made the platinum more difficult, though, since they could've made it so you have to earn all non-DLC titles for the characters (which would've bumped it up another *, IMO, because some are a pain to get).
