I'm having doubts now. It seems that damage and healing scaling gets worse with every expansion. Any priests tried healing at level 3? Yeah it's overpowered. Just cross your fingers that blizzard will scale things better. Because if level cap scaling gets fixed and the 20s doesn't, then this bracket is over.
Another thing to point out is the reason I found why Blizzard makes low level pvp unbalanced. They are trying to encourage players to level to cap and try not to pvp at low levels at all. I see it clearly because some low level pvp problems can be easily fixed by moving concussive shot to level 60 etc.
Only my opinion. After all, Blizzard doesn't give a damn about twinking.