I'm afraid there's not really much SE can do, but please keep reading I will try and explain why. Also 15 posts actually isn't that many if you think about it. SE don't publish how many active subscribers there are, but the general estimated figure is around 500,000 so 15 in that many... (obviously not everyone with connection problem reports them here and I think there's more than 15 posts too, but I think you get what I'm saying).
Not every Internet server is located in the same place. I see that you you are on Tonberry and the game servers for Tonberry are physically located in Japan. I have no idea where you are located, but since you're English speaking, there's a high chance you're not in Japan (apologies if that assumption is wrong!). So whenever you're playing the game your Internet provider has to create a route for you to get from wherever you live all the way to Japan and unfortunately it sounds like at times some of the routes you are going on are congested/have problems.
Square Enix has no control over how you get to them, that's completely down to your Internet provider. Alternatively when ISPs won't change routing (most of the time sadly...) some players use 3rd party VPN software which manually adjusts the routes to try and avoid bad network points, but again this isn't something SE can control as they have no control over your Internet connection. You're connecting to them, not them to you.
So the reason you don't have problems with other games is that their servers are probably located somewhere else (probably not even in Japan, although that will depend on what you are playing) so when you connect to those servers you taking a completely different route.
For your reference the NA servers are located in California, USA and the European servers are located in Frankfurt, Germany. If you are physically closer to any of those you may wish to consider if transfering is an option (or at least try with another character), but I appreciate that may not be an option and you may have picked Tonberry for a reason.
I hope this has helped to explain and why you need to do a traceroute to find the problem/report it to your Internet provider.