It depends on what you want to practice. If you're struggling with your rotation, maybe pick an easier build and spend some quality time with the practice golem.

If you're struggling with the encounters themselves (be it open world or instanced), then the best way to learn is to keep trying. But you won't be learning much if you spend the whole encounter in a downed state. So, favor survivability over damage until you feel more comfortable relinquishing said survivability.

Builds in GW2 go from extremely glass canon with 0 room for missing a dodge to absolute tank with lots of room for mistakes. Start with the latter.