Desync is when the information you send to the server is not the same as the information your client is reading. So you may walk around a rock to the left on your screen. The server says you walked around it to the right. Now you teleport back to before the rock so that the server can re-sync you to the information the server had on your last known location.
Well I recently received a beta key to their newest and biggest expansion ever done. I can finally say with certainty that desync has been fixed. The game feels really smooth. The expansion will come out of a closed beta late June or early July. Hope any of you that are ARPG lovers finally find something you enjoy playing.