I think the important thing with accents is to make sure they feel congruent with the rest of the setting, because otherwise they will be real immersion killers. For example, I absolutely loved The Witcher (all three of them), but I found it quite jarring when everyone else has various forms of British accents whereas Geralt and his friends strut around with very strong, American ones. Meanwhile, in Dragon Age all dwarves have American accents and thus it doesn't stand out in the same way. Pillars definitely falls into this second category, and while it took some time to get used to, I honestly don't mind it at all. One thing I like to think is that unless explicitly stated otherwise, the spoken language in fiction isn't really English: it's translated from whatever the "original" language was.
This is the way Tolkien went about it in his works. English is used in place of Westron, the common tongue of Men (and Hobbits) in Middle-Earth, and even names are translated. Frodo's actual name was Maura Labingi. Samwise Gamgee was actually Banazir Galbasi while Merry and Pippin's full names were Kalimac Brandagamba and Razanur Tûc respectively. Following this logic, it really just means that while the modern Aedyran language is represented by English, it isn't actually English as we know it. The American accent just so happens to correspond to its Dyrwoodan counterpart.
