Brackets defeat the idea of RANDOM Battleground (Granted, that's the least of an issue.) Last time that I played BGs it was mostly the same faces in quite a few bgs in row, reminded me of Moltens Lordaeron when it went to 2k people on peak time. On top of that, while yes, premades dominated the BGs they're in for the most part before as well, a lot smaller pool of players means that you have a lot higher chance to meet a premade than when there were no brackets unless you went specifically for AV, and even then.
Overall, BGs were always there just to screw around and have fun with, and everything that was "added", except Mercenary just kept chipping on the fun until it just is boring/annoying.