It's probably your connection; when I use PvP Duel for events like Tournaments and War, I rarely encounter desynchs.
On a sidenote, if you happen to play a particularly annoying deck, you may find that people start ragequitting after a few turns

Otherwise, I would say that your connection's a bit on the wonky side.
Check your connections here:
http://www.elementsthegame.com/connections.htmlIf your ping to the servers is really high, then it makes desynchs more likely to occur. Also, when you're playing PvP, don't switch to different tabs or windows; doing so has been attributed to some degree of desynching before.