As Obnoxious pointed out, you might get the exact opposite effect. Now instead of one "carrot" for HK farming, they have the additional "carrot" of an easy victory. As far as I know, premades already get prioritized against premades, at least this appeared to be the case in the past. This has ironically caused people like me to purposely avoid playing Random Battlegrounds with friends.
If the goal is to have a diverse team roster, simply randomize the teams regardless of race, faction, gear, skill would work.
This is essentially what is already happening, and premades are crushing randoms with similar gear levels. This is hardly a surprise given premades are typically superior in terms of composition and skill level.
Just want to point out that RL spamming "ALL MID", "ALL TOGETHER", "DON'T SPREAD", "REPORT XXXXXXX" (presumably for trying to do the objective) ... etc., is the lowest form of teamwork there is and shouldn't even count as one in the context of battlegrounds. Also, depending on the time of the day, it is not uncommon to get the infamous "AV, AV, IoC ..." chain while Horde runs their premades. The chances for casuals to run into premades can actually be quite high during certain hours.