Brawler’s Guild requires good gear besides skills.
I have managed to reach the final boss from rank 5 by using only PVP gear, half blue and half epic. Fully upgraded, enchanted and gemed.
Still, there have been some fights where dps was all that mattered. And I can’t kill the boss from the last battle from rank 5 because of not having enough dps.
The first 3-4 ranks require just skill. After that, dps will become important, especially in some fights. Blizzard has designed the fights that some will be about dps and some about movement. I think the last battle from every rank is a dps checker.
If you plan to try Brawler’s Guild, I would recomend to gear your character, playing in questing gear is out of the question. Getting past rank 5 will require gear from LFR.