I was about to come here and ask the exact same thing. I have been enduring it ever since DT launch. I have never had a connection problem with FF14 before now. I'm east coast usa, not sure if the location matters at all.

I asked in a frontlines match if anyone else was having these disconnects. (I load into pvp very slow, like 1 player at a time after DT launch will pop in showing more connection weirdness between me and the rest of the frontline). They said it had something to do with my graphics card? I didn't quite understand the connection the other players were trying to make between GPU and networking issues... but that's the only input I have had form other players about it.

ETA: They were implying because DT introduced a graphical update, people with older GPU's like me will be dealing with lag now for ~reasons~