To directly answer the thread title, shields are absolutely not needed as long as you have your rolls and most enemies are less than perfect when it comes to navigating over or around obstacles. Besides wolves and deathsquitos, most enemies can't even match your straight line running speed, which you can further improve through skilling up.

However if you are rocking a one-handed weapon then parrying is a no-brainer from both a DPS and crowd control perspective.

If you are using the two-handed weapons you may as well exploit their reach for all that they are worth so that you can stagger your enemy through a barrage of attacks instead.