Miranda is always a fine choice because of her ability to cause explosions and also because she can enhance the team´s abilities.
Zaed is another great choice because he has insane weapon damage. He and Miranda will also work greatly against synthetics (overload+zaed´s special ammo).
If you have Garrus with area overload+plus armor-piercing ammo shared with the whole team and also has miranda or zaed as support you can wreak havoc on the battlefield.
I realize that it´s an unusual choice, but both Tali and Legion can also assist, either by hacking some enemies or by using drones to distract the enemies. With 2 drones on the field, the enemies will have to deal with 5 hostile opponents instead of the usual 3. The only problem is that even on maximum level the drones take forever to reload once they´re summoned.
But to be fair, I´m far from being a vanguard specialist. To be completely honest it´s my least favorite class on single-player in the entire series. While I do find all other classes fun (and funny) to play, vanguard was always a very tense experience to me. If I try a trilogy run with the vanguard, I´ll probably need to reload the games more times on this particular play-through than all the other 5 classes trilogy runs combined. I´m not joking.
I´m not a fan of the high-risk/high-reward mentality. I rather play safe and from a distance, only engaging at close range targets at opportunity or when there´s no other way because the fight already starts with the enemy right on top of you.
I also have to say that I don´t like shotguns in the me2/3 era. Not when ammo becomes an issue. It´s an issue with snippers too, I know, but at least I´m far away from the enemy trying to find more clips.
Otherwise, I´m usually a snipper (even if I´m Soldier class), or using biotic and tech powers from medium or long distance.
The only thing I think I could add is that the choice of squad-mates (as well as the way you evolve their powers) depends not only on the class shepard is using, but also the difficult level you set for your game. Some choices of evolution can work in reversal order if you´re playing on casual or normal, compared to someone playing on hardcore and insanity. In normal, you don´t have to worry about stripping enemies defenses during most of the time. Very few elite enemies, sub-bosses and bosses exist. The mentality of a player on the harder levels needs to be radically different. You wont be simply dealing with a more aggressive AI that causes more damage and utilizes special powers more often, but enemies mounted with defenses that need to be dealt with. As you become more proficient with the game and advances to replay it on harder levels, instead of merely intensifying your strategies, in some points you also need to alter them.