Most of the players who play this game are casuals, this include those who queue for Random Battlegrounds. While premades may make up a sizeable chunk of PVP players present in battlegrounds at any given time, they are hardly the majority. Typically what happens in an imbalanced premade vs "randoms" match, is at least half of the "randoms" will get replaced, sometimes several times over depending on the length of the battleground and the severity of its one-sidedness. Also, it hardly takes a full premade to cause severe imbalance in battlegrounds. I have seen Warsong Gulch dominated by two-man DPS+Healer combos. There is little doubt that a team composed of merely 30-50% premade will hold a significant advantage over a team of random players.
But as you pointed out, this is exactly why premades are formed --- to gain an advantage over other players. From the point of view of most casual player, this is extremely unfair, and if they were able to form quality premades, they wouldn't be considered casuals in the first place. Forming premades requires a lot of work and is time consuming. That is why there are PVP guilds dedicated to such activities.
There is a difference between changes to game mechanics (or class balance) versus quality of life improvements (conveniences). Most people who come here to play 3.3.5a are willing to put up with the latter but not the former. Let's stay focused and address the issue at hand. This thread is about battleground imbalance caused by premades.

