Even in single player you are still playing on a remote server. The desyncs are fairly minor. I play in Hardcore exclusively (you die and that's it) and I haven't had any issues despite winning the game and moving up to the final boss on the second difficulty.
Understand the POE ends up being a lot about wiping out large packs of enemies, so AOE is pretty standard for every single character. As a result, a desync of a mob a short distance doesn't save it. It certainly isn't ideal and if memory serves D3 is much better about that not happening. But the desyncs aren't really a concern for me.