Absolutely not a commentary on people with disabilities IRL. This is only something I only wonder about in terms of DA lore.
For people that seem to be pretty much incapable of charity and compassion, since their philosophy strictly prohibits free thinking and all that, why are the qunari so uncharacteristically compassionate to people with disabilities? The tamassrans are tasked with taking care of people who are too mentally or physically disabled to function independently in society. Yet supposedly people are viewed as a resource like any other (water, stone, wood, etc), so why would they care for people who are unable to function as such?
Would they ever accept people with disabilities from other cultures as converts?
The Qun waste nothing. Even people with one or more physical, mental, or even social disability have things they can physically, mentally, and/or socially do, so the Qun focuses on what they CAN do, and likely assign them a job they can do well, rather than focusing on what they CAN'T do and defining/dismissing their entire existence based that one thing (like you seem to be doing).
For example, deaf people might not be able to hear, but they can still use their eyes and hands just fine. Rather than just saying, "You're deaf, you can't do it" (an attitude which MOST deaf people live with every day of their lives in this society), the Qun would likely evaluate them, find out what they can do, maybe even discover that with proper aid they can do something really well (for example, a deaf person can work well with a group of hearing people if they have an interpreter to translate their visual language to spoken language and vice versa), then assign them that job and/or give them the aid they need to do that job well.
I work with deaf people every day, and I have a blind friend, and let me tell you, our Western society is NOT the pillar of "charity and compassion" you think it is. At least, we are notoriously ableist ("You can't do this because you're deaf") and paternalistic ("Oh no, you can't take care of yourself, you NEED ME to take care of you because you're a helpless child without me") toward people we deem having "disabilities," focusing more on what they can't do and restricting or shunning them for it, rather than focusing on what they can do and enabling their talents to the best of their abilities.
I can actually see the Qunari culture being more accepting of people with "disabilities" because, as a culture, their whole shtick is finding out what people are good at and assigning them jobs they can perform well. If providing a physical caretaker to help someone who's not so great in one area (an "interpreter" of sorts for a deaf person, a seeing-eye person for a blind person, a caretaker for a mentally handicapped person, etc), helps them do well in an area they are good at, so be it.