Highly dependent on class and spec. Tanks can solo them in questing greens. Others need more gear to be comfortable.
It also depends on player experience. Delves require more knowledge of your utility tree than most other activites.
Week 1 I was running a t11 Earthcrawl on my 676 Boomkin, who are not known for their tankiness. While pulling a nemesis pack, Brann got knocked into a 2nd pack, pulling them. Then Ky’veza attacked. It took a lot of fancy dancing but I managed to be the only one standing in the end.
I’m overall not a very good player but I’ve been playing her since the dawn of time and know her buttons. I’ve also run an absurd number of delves.