I often see people assume humans are conscious because we are more intelligent than other species, but we have already developed AI capable of processing data and making decisions that would dwarf the capabilities of a modern human. Yet, no consciousness as far as we can tell.

I would argue this is kinda faulty reasoning. Everything AI knows how to do is because a human told it how to think through coding. It's not smarter than humans it's just faster. Give a human enough time, and it can do the same calculations.

. The organisms we have found to pass the "mirror test" or even come close are all social animals.

While I agree humans being social have been key throughout our history you kinda disprove yourself by bringing up "mirror test" as the animals that recognize themselves in the mirror are generally regarded as extremely intelligent (Elephants, Pigs, Dolphins, Parrots, and Crows) 
Another thing you brought up is language. Is that not another sign of intelligence right there? Parrots are seen as amazing smart for being able to speak and then look at humans with are insane amount of different languages with their own rules and dialects.