some of the trash is quite potent.
You'll want to make sure you have a round robin for spell interrupt, they are off the global cooldown so can be used at anything while still dpsing. There are some mobs that cause some nasty side effects.

When I first rolled into legion the dungeons took me by surprise as well for how hard they hit. The gear gap from a fresh 110, to having artifact traits and gear is a huge difference. Once you get more under your belt at max lvl it smooths out.