There is a spot in the back where you can't be hit by a brute's backswing. Generally though I find the best solution is to farm out fade touched dawnstone for that 5 seconds of Walking Fortress proc chance. That masterwork is great for making sure you're not knocked around.
Early on in the game (Basically the far west and southwest part of the hinterlands and the Hand of Korth fight) I generally don't screw around auto attacking and only go in to toss in a Twin Fangs or Deathblow out of stealth.
A mage spec'd in winter can lock them down for a while too. Ice mine's freeze lasts forever and if you have the only detonation, you can get the most out of the freeze duration, then shatter them.
Funnily enough, Deathblow's 2nd hit can cause knockdown on most of the brutes in the game from behind.
Just don't attack from the front though.