Taking this to the AT&T forums will only move an issue that isn't necessarily Square Enix's fault from these forums, to a place where it isn't necessarily AT&Ts fault. This is an issue that is primarily NTTs fault, either in their own equipment, or in equipment which they have purchased or leased from another vendor (possibly AT&T, if they wish to claim so). However, even if that were the case, it would still be NTTs fault that the issue is still present if it is not affecting other major ISPs, as that would imply that there exist multiple inter/intraconnects between their Dallas and San Angeles DCs, and they continue sending primarily AT&T customers down a known bad line.
I still stand by the "everyone sucks here" approach. But it definitely doesn't hurt to light a fire on the AT&T forums as well. I'm not saying to abandon this thread or to stop sending reports/tickets to SE, that definitely should still happen.

The blame just keeps getting passed around. As AT&T customers, we can pressure them. As customers of SE, we can pressure them. Where is the issue most likely? NTT. Who can pressure NTT? SE for sure (they pay NTT right?), and probably AT&T as well.

We all want the same thing, to play the game unimpeded by this NTT latency and packet loss, as we had been doing up until last week. (at least for me, I'm aware these issues are far more rampant for others)