You will see a lot of variation in survivability depending on what dungeon you play. 50/60 dungeons don't really have an appropriate gear sync so you can pull huge amounts of enemies without taking much damage if overgeared, but Leveling dungeons with a tight sync can wreck people if they pull a lot. As you put in more hours of time you'll come to recognise which sections of which dungeons need more intensive healing or mitigation and better prepare your cooldowns and pacing. Bit more refined every day you practice.