That's a piss poor argument, Symphonia's cast were just the same, a bunch of new Tales characters no one was supposed to give a **** about until they played the game. They could have just as well replaced them all with the Phantasia cast, which isn't inconceivable considering that they're actually in the same game world canon ad have used time travel.
Also bitching about the spirit Ratatoskr is just silly, it had no direct role when it came to Lloyd merging the worlds, therefore it's not really surprising to me that no one really knew about it considering that Lloyd + company aren't exactly experts on merging and splitting entire planets with a super sword. They're not going to lay out the entire plotline of a sequel that most likely wasn't planned in the original, that would sort of make the sequel redundant when you know every detail right from the start. If they knew about Ratatoskr, it would make even less sense for everyone to start looking for it now after two years.
Also, why the hell would Namco use Symphonia as a "sales gimmick"? It's not even the best selling Tales in Japan, if they wanted to milk a popular Tales they would be doing it with Destiny.
Ratatoskr Knight seems to be doing everything right with a sequel, introducing new and interesting characters ALONGSIDE the returning cast, and improving gameplay in all the right aspects, yet it seems like people are dying for a reason not to like it. It could very well be better than the original ToS but I'm afraid it will be submitted to this mindless bashing all of it's life simply because it's a sequel and sequels are not allowed to be good.