My justicar is fine by herself. If you throw reave, then shoot twice with the carnifex and repeat you can kill Brute REALLY fast. You guys know that Reave's damage stacks right? of course she is way better with help, but she is essentially a biotic soldier with good sheilds plus Reaves defensive abilities, and great offensive abilities too.
I always try to use pull on random normal soldiers in packs and use them as biotic grenades, its saved me quite a few times.