Didn't Minaeve also say they can't even feed themselves? Really, it seems Bioware doesn't know how tranquil should act
Not, as far as I know.
Here's the transcript of her dialogue about the Tranquil;
Inquisitor: "You said you were keeping some of the Tranquil safe?"
Minaeve: "Yes, the mages took some of them when my Circle rebelled. The rest were forgotten. Most Circle mages look down the Tranquil or try pretending they don't exist. They don't have any emotions, they can barely take care of themselves, can't defend themselves at all. It's a shame, I like them better than most people."
Inquisitor: "I'm glad they have someone like you."
Minaeve: "They deserve better. They're polite, they're rational and they never get angry at you. When they study, they have a focus no normal person could ever match but the Templars, even some of the mages mistreated them just because they could. The Tranquil never fought back."
Here is what the Wikipedia says on the State of Tranquility;
In the mind of the Tranquil, there is no passion. They keep to themselves, and, if asked directly, will readily agree that having the opportunity to live out a peaceful and useful existence is far preferable when compared to what their alternatives would have been.
The Tranquil are stripped of their capacity to form anything other than a logical opinion. However, they neither lose their memory nor become automatons: they possess free will. They do not wish to die (unless it's for a cause they believe in and are no more susceptible to suggestion than they were previously. They are more agreeable and would not normally oppose an authority figure, because they do not possess the desire to object, but if the Tranquil see a logical reason not to follow an order, they do so. Tranquil can't take offense and know no modesty.
Tranquil can be creative, insofar as a very logical scientist might be. They pursue a means to an end, and are capable of coming up with alternate solutions to problems. They are, however, methodical to a fault. They are not taken by inspiration, and some might say what they lack is intuition. The fact that they do not get bored and take no pleasure out of creating takes much of the impetus away for them to change their methods or seek to create something different unless there is a clear reason to.