Well, the one thing I've always noticed is that well-rounded trumps specialist in basic combat. I'm not saying that a specialist isn't going to be amazing, but in the case of a team, I'd be bulking up on soldiers as my primaries. Probably go four soldiers, two engineers, one medic one operative. Medic stays well back...operative is on his own.
Good observations, I agree although I think I would take it further.
The first thing I would point out is that, in the case of Brink, Soldiers are a form of specialist as well. We all carry guns, can fight, etc. A Heavy Engineer with a minigun might be just as effective as a Heavy Soldier with a minigun, aside from the class abilities.
My thought is that weight and weapon define the "team" play more than class in many cases, so my line up might not break down quite the same.
I'm thinking along the lines of an 8 man team divided into a primary "frontline" force of 4, a loose 3 man team, a single.
The 4 man front (alpha) includes a mix of heavies and mediums depending on weapon skill with
2 Gunners (soldier or Engi ideally) with MGs or ARs to either supress the attacking force (when on D) or press forward on offense.
1 Medic (preferably an accuracy player) with an AR to keep his front men covered and so he can move in and out to heal as needed.
1 Heavy Crowd Control (another soldier or engineer) with a Grenade launcher to keep his front from being over run.
The 3 man team (bravo) covers alpha and plugs the holes to keep alpha from getting flanked in attack or defense. Mediums or lights are more ideal here for speed and movement. They don't stay with each other neccesarily, but stay in the same "Zone" so to speak.
1 Engineer with shotgun and good turret ability
1 Operative with a mix of close range and longer range weaponry, specifically set up for Counter Operative play
1 Medic with good close to mid range gear. He covers both Bravo team and any clean up needed for Alpha.
And the single is likely an Op sent out to screw with the enemy and keep them guessing.