To be fair, the whole ‘original’ thing came about because AshlikeSnow lorded it around as it being the only way FFXIV should be. If a character talks differently (“thou art strong, mortal”), then to them, that is apparently the localisation team failing to be faithful to the Japanese script to some extent. Person in question appears to also believes that medieval speech is all there is, when that’s really far from the truth (unless they've changed their stance and conceded, then good for them). There is ye olde, but then there’s also yar pirates, ‘normal English,’ cockney, Victorian English, etc.
Alrighty, I’ll concede with the Haurchefant… though to be honest, I still like what we got in the end (and it seems many others feel the same way). Reading into that, though, it seems that the localisation team must always get their work proof read before anything is put into the game. They also ask questions and such regarding a character and cutscene and see to it that everything is right with the plot/lore. This means that the English localisation team was given the okay to have Matoya being cheeky (not harsh, unless there was more after that ‘flirt’ quip) with Alphinaud. This also means they are given the okay for the choice in multiple dialects.
And you are entitled to that opinion, but remember that Eorzea has multiple cultures that tend to borrow from English history and I’m sure even in Japanese they try to fit the dialect of the location (makes me wonder how the pirates of Limsa Lominsa speak in Japanese). Also like I said before, the English localisation team pretty much works with the Japanese team as they’re making the world and story, so the team(s) are going to ask who this person is, what their gimmick is and where they sit in the story and if they’re given the okay to give that character a little spice, then that’s what they’ll do (Matoya being cheeky) and you cannot fault them on this as they ASKED.
I am pretty darn sure the English localisation team will be asking a lot of questions for the day we ever step foot into Othard, as that place is pretty much the Asia of Hydaelyn (so we can potentially expect Asian dialects there. Which specifically? we do not know).
It's much easier to go back into history and look up old (and current) dialects that may fit the character and setting. Easier to match a voice for the culture, so to say. I’ll admit that Urianger is pretty hipster in his ye olde speech, when everyone else around him talk normally (it makes sense for Primals and dragons, as they’re kinda from ye olde times. Maybe Ascians, too). At least we have some made up languages in the game, being Dragonspeak and to some extent, High Sylphic (currently only heard in Ramuh’s lyrics?).
Unrelated edit: I was going to keep all your arguments in the quote bubbles, but... well, that'd just make my post unnecessarily too big, don't you agree? Cleaned it up.