I have said it before and I'll say it again VPN services only use a private network to get to the destination rather than the internet if a VPN works the issue CANNOT be SE's issue because you are connecting to the same severs, through the same ISP for SE, the only variable you have changed is using a private network and a managed route.

What you need to do is contact your ISP see if they are throttling FFXIV traffic for some reason (entirely possible) tell them a VPN improves the game experience, then they cannot push the issue on SE.

If you reject my ideas please tell me how it's SE's fault that your ISP might be throttling traffic, or using a less efficient route to the datacenter (both of which are solved using a VPN).