So I've been cursing my laptop's wireless card for the lag spikes I've been having when I play at night, making bosses impossible to survive, and now I find out it's been the fault of Verizon FiOS throttling the XIV servers since they're the same types of servers that Netflix uses.
I've been recommended by fellow throttles FiOS users to download WTFast for $10 a month, which will fix the issue. Going to call Verizon and demand they drop my bill $10 a month to compensate, as I upgraded to a rip-off $99 bandwidth level in hoping that would fix the problem before I knew they were the problem.
Screw Verizon.
I have FIOS and the same lag/packet loss issues with this game. Only way it's playable during peak hours is through a VPN.
Though from what I understand it's not really a question of Verizon throttling you, but rather their poor routing to the NA servers located in Montreal.