I recently came across a comparison of the English and Japanese texts for the analects in FFXIII which as you should know, contain excerpts relating to the mythology and history of the game's universe. It's fascinating stuff, until you begin to realise that the English version is just inferior to the Japanese because some details are translated in a way that they're rendered ambiguous and unclear. I don't have the link anymore and neither do I have a specific example in my head unfortunately, but it's a reminder that sometimes localisation can suffer in places not immediately clear to the player.
A script that suffers here and there isn't going to significantly tarnish a game experience for me, and I acknowledge that at times, something that sounds stupid is a result of the Japanese script also having a bad day at that particular instance, though it shouldn't stop a translator from taking some creative liberties to make it sound less silly. I remember Serah at one point in FFXIII-2 being confounded that a certain elevator to Cocoon which isn't due for completion until a few years later, is finished and up and running...even though she clearly went through a time portal with Noel and they both acknowledged it. Keeping this makes Serah needlessly seem like a slight moron. It's minor I know, but such is the task of localising a whole Japanese RPG anyway.
To also hear that Realm Reborn has...questionable voice acting and voice direction is disconcerting. It makes me wonder why, especially when in my opinion the voice direction never had it so good when it came to FFXII. Lightning's voice grows increasingly more monotone with each game and until we start hearing some actual English voices for FFXV, I'm a bit concerned about that side of the localisation process. They can do it, but lately it smells like a bit of complacency and questionable choices. If it's bad and the script is bad as well, it doesn't matter how much great voice talent you have if what they have to work with negates how good they can sound in the final product.
That being said, I still think FFXII's localisation is undoubtedly the best in the series, evoking that sense of authenticity you would expect to see in a setting like Ivalice. The script is a bit confounding at times, and not for the average layman to instantly understand. I suppose it can come across as a wee bit pretentious as well, though funnily enough I respect the fact that there are a few lines that make me think of Game of Thrones, like "mummer's farce".