Charge + Nova gives the player an out regardless. The only class that would ever not have an out, is a Soldier who ran out of ammo, or a really poorly built Sen on Insanity. Which isn't really all that different from a poorly built Sen on Insanity in ME1 really.
The preset lists prevents the power abuse of choosing any power. Otherwise anyone could choose Warp + Throw, or Overload + Incinerate, and still have their base build to augment it. That works for Adepts and Engineers, because, even though they have big detonations and Combat Drones, they don't get massive weapon damage boosts in their base skillset.
Being able to choose Explosive Ammo + Overload + Incinerate + Tactical Cloak with Weapon Damage +50% from armor pieces, just makes for a completely broken class. My goal is to offer player freedom, while mitigating how overpowered combos can be abused.
Yes, a Vanguard with Pull + Throw, or Pull + Reave (which is available in ME3) does end up worse at biotic explosions without a Warp user around, but they shouldn't be as good as an Adept with Singularity + Warp, that's the point, they get Charge and Nova, in addition to more weight to put towards weapons to counteract the fact that they're worse at biotics.
Let's say for example we have a Vanguard. They can take 2 of the following, Pull, Throw, or Reave, Shockwave That automatically gives them a detonator, and a primer. Both for themselves, and their teammates to use. They still have Charge + Nova if they don't want to sit back and play as a sub-optimal adept, but they have a built-in combo too.
Pull + Throw creates the bigger explosion, but doesn't work on enemies with protection, and throw can only be used to detonate, pull only to prime.
Reave offers an option against enemies with defenses, and can set up a throw combo, but has the longest cooldown time, and the smallest AoE (it doesn't, but let's say it does here).
Reave + Pull doesn't work on protected targets, creates the smallest explosion, but gives you an option against enemies with physical Shields, and Reave can set up a Charge/Nova combo, sacrificing cooldown time, for a primer on protected targets and AoE.
As it stands, the only difference between that Vanguard, and ME3's Vanguard is that Reave is a bonus Power, and I traded Shockwave out for Throw. It's not like it turned the Vanguard into ME1's version, which literally was just a weaker Adept with the ability to reset its cooldowns and a shotgun. It's the exact same class, except now you can sit back without having to take Reave as a bonus power, just replacing Shockwave with it. Then you can charge in when you've picked the group of husks (or their counterpart in this game) off, to start shotgunning/novaguarding/whatever, the big enemies.
Edit: You can actually come pretty close to that Infiltrator build in ME3. Replacing Overload with Shield Drain and Incendiary Ammo for Disrupter Ammo. Add in a shotgun (Spike Thrower to break Shield Gate), the Paladin, or Black Widow/Javelin/Widow for max brokenness.