I like that the companions have their own hook and storyline. Sorry you want "generic grunt #2". In D&D adventurers are a rare lot and few people even have classes, so them having a story isn't an issue. Maybe they can have let you design your own mute henchmen like in the Pillars of Eternity games?
I swear D&D nerds are allergic to fun.
SPOILERS
One extreme is as distasteful as the other. It isn't that being exceptional is inherently problematic, it is that exceptional exists in relation to a norm, and both have to be representing for either to have any significant impact or meaning. Having a survivor of a goblin sacked town bent on revenge would make an understandable and relatable companion without stretching anything. Personal quests could involve gathering enough coin/resources/territory to establish a militia/memorial/hire-foreign-mercenaries, or simply making peace with what happened and moving on (like after the upteenth time the player has committed their own private genocide and they are forced to reckon with what they have become). Interesting is a matter of depth, not breadth. So much happens even in the little covered in the early release there are dozens of motivations to be found. When you meet the dying Strong Soul and the two apprentices, one could choose to accompany you, their personal struggle being between their confidence and trust in the player and their belief in the Absolute. Or maybe both could, and then they are at not only at odds internally but also with one another which could prove very interesting. At the gates of the Druid enclave, one of the three individuals you save (assuming you saved them all, I did) may elect to join you as a debt of honor, knowing they could never have survived without your intercession and their personal quests could involve tempering their sense of duty and obligation with graciousness and generosity. NPCs can be compelling and sympathetic without being unicorns, in fact, many here (and in other threads) seem to agree that unicorns aren't really all that interesting when they are everywhere.