I am having this exact same issue as well. A little bit of backstory the game ran perfectly for me on maximum settings until the day I downloaded the complete edition (had just hit 50 on my main) and once the download was complete the game has been almost unplayable. Massive lag spikes, framerate drops, etc that lock the game up for multiple seconds in general. It doesn't happen with any other game including MMOs and I used the FF14 benchmark and it said my computers performance was extremely high (and that was with the game running in the background randomly lagging out). I'd love some help with this otherwise I'm afraid I wasted my money on the expansion as I wont be able to play the game let alone keep my sub.