People tend to try to "discredit" some people's desire for genuinely evil/selfish/cruel actions by painting said actions as "stupid" evil. Nah. That requires a severe overestimation of what the spectrum of "stupid" evil covers. Stupid evil is while a ruler hands you a quest to go kill a dragon, you decide to charge at him, even though he's surrounded by his elite guard in full plate armour, while you're dressed in rags, just so you can get his shiny crown.
Knife murdering someone in an alley or the top of a mountain, where no one can see you or blood sacrificing the elven slaves for power in dao, while your companions are around is not stupid evil. Being selfish and cruel isn't necessarily stupid, stupid comes when you have utter disregard of consequences. Given that most companions can hold you in extremely high regard or are indebted to you for sparing their lives, saving their pupils, having a maker-given vision of you or whatever, expecting them to suck it up when you're evil, provided you don't attack someone they personally care for is perfectly ok, imo.
The same could have been done in dai, simply by making the anchor activate consciously only and not by proximity to the rifts, then the story could easily support your advisors and companions accepting your evil actions. It was doable and wouldn't cheapen your companion's character, it just wasn't in bioware's interest.