The truth is that a lot of players I see in regular warzones simply don't understand how to or perhaps want to play their role to help their team... if I had credits for every time I saw a juggernaut in a tanking stance with zero protection at the end of a warzone I'd be rich. Having a guaranteed number of healers in a game and a limit of heal spec'd players would be beneficial to games though.
I know when I've solo queued on my healers I've ended up on teams, multiple times, where 5 of us were fully heal spec'd... I queue as dps and routinely never have even one person traited to heal. It's frustrating to say the least, especially when the other team has three healers. When I've queued as a deception assassin I've ended up on teams with 5 other deception assassins in a voidstar.. needless to say the other team got worked pretty hard.
It's just small things they can do to make games interesting and enjoyable for both sides as no one likes getting rolled and people genuinely like to feel like they should have a chance at a similar odds.