I refuse to ever kill something for the first time unsynced (or with Echo or gear higher than was available at the time etc.). For me that defeats the entire point of having a challenge in the game. Sometimes that means I clear stuff very late, but I assure you it is possible to do.

It's not for me to tell others how they should play or what they should value though. I'd never try to stop anyone else from unsyncing if they don't feel the same way.