In no way can it be seen that deafness is a blessing. As a person with a deaf mom, I know from experience. My mother tells me that she hates being deaf. Although she can hear a little bit, she misses being able to hear better. When a person is hard at hearing, he or she also has trouble taking part in conversation and listening to music or movies.
People can have a very fulfilling life with a disability like deafness but it is still a burden. It will weigh on them in ways that people who are not deaf can't not understand. And they will be looked at differently because of it, especially if they are in high school. I would like to think that humanity is universally accepting and it's the few and far between bad eggs that ruin it for everyone, but that has not been my experience.
No, I do not think that deafness is a blessing, because the person can do less than the ordinary person does. If it were someone's choice not to hear that would not be a curse. However, being deaf is something that just happens. When it does, the person has challenges to overcome and more things to learn.
When you normally think in terms of ‘blessings’ and ‘curses’ you think in terms of something preternatural; the question doesn’t outright ask this, but it is implied. Because of personal beliefs, I have to say that it is neither. Blessings are the giving of something ultimately positive and curses are the exact opposite, but with the intent to teach a lesson as well. Deafness is neither ultimately positive nor ultimately negative with the intent of teaching a lesson to anyone that is born with the condition or develops it. Instead, I think it is better to look at deafness the same way other physical limitations are seen; medical conditions. There are pros and cons with the condition though the negative is more pronounced in the minds of those not suffering from it than those that are. Deaf people are often described as having more finely attuned peripheral senses like sight, smell, touch, taste, and to a lesser degree balance (which is, according to studies done, the sixth peripheral sense in the limbic system). However, not being able to hear sounds or tones deprives a person of certain experiences which is a tragic negative. The bottom line: curses and blessings are finite in their being positive or negative; medical conditions are not defined in the same sense.