Assuming you are right (which I am not convinced of), there is still the question of whether those three will each uniquely fill one of those four classic D&D party roles? If that criterion is also amazingly satisfied by those three companions, that still leaves me with only being able to play, as my PC, that one party role left uncovered by those three companions. So, for example, if those three "good" companions are damage dealer, controller, and healer, then the best scenario I get from BG3 is that I must always play a tank PC.
So the most likely classes for these 3 companions are Ranger, Barbarian, and Bard. These classes can fill the 4 roles you've defined.
Barbarians are by far the best tanks in 5e since they have most effective hp out of any class. They can also serve as good primary and secondary damage dealers, especially when 2 handing.
Rangers are also a good class that can play multiple roles. They typically have high dex which when combined with a shield, some good light armor, and the defense fighting style means they can serve as decent frontline tanks. They can also deal good damage and are half casters which also lets them serve a limited role as controllers.
Bards are full casters who have access to a good number of spells which includes healing word AKA the best healing spell in 5e. They can serve as healers, primary/secondary dps, buffers, and controllers. They're also the best skill monkeys in 5e.
It's also worth keeping in mind that dedicated healers aren't really necessary in 5e. Healing is very inefficient and past tier 1 it's extremely rare to be instantly killed which means that healing word as a way to instantly stabilize and revive PCs as a BA is a much better option than spending a full action to heal their wounds.
