In my setting, one of the habitable (?) worlds has a global average temperature of 34 degrees Celsius (93.2 F). Is this within the human habitability range, or is it too hot?
The average temperature of Earth is ~15 degrees Celsius. So, your planet is about 19 degrees warmer than Earth. I suppose Dakkar would be uninhabitable if it were 19 degrees warmer, but Helsinki would have a temperature similar to Miami. Seems livable to me, though if its life forms were autochtonous, life in each hemisphere would probably differ a lot from the other side.
A global average temperature of 34°C would be very uncomfortable and have expanses of areas uninhabitable by humans, but it would not preclude human life in some areas. The bigger problem would be understanding wet-bulb temperature. In a civilization with advanced technology, interior areas could be made habitable, but there is a limit where it becomes impossible to survive in the unprotected environment, even if not working/moving.
For that limit, the humidity of the environment influences the ability for living organisms to radiate the heat that they produce. From this article on the impact of temperature and climate change on survivability:
The wet-bulb temperature is probably not a very good predictor of the "feels-like" temperature for most common conditions, which is why it is not used for this. However, it can be used to establish an absolute limit on metabolic heat transfer that is based on physical laws rather than the extrapolation of empirical approximations. That is why we focused on it instead of the usual measures.
So, more parameters are required to understand how survivable your world is to humans.
Life on Earth lives in a delicate balance. The rise of only a few degrees C would spell absolute disaster if it happened here. On Earth, the average temperature is slightly less than 15 C (58.3 F). This means that the average temperature on this planet would be roughly 50% hotter. Over the past several decades, Earth's average temperature has risen only about a degree Celsius, but that small change has had a huge impact on weather patterns, as well as the melting of glaciers, and polar ice caps.
If the average global temperature is 34 C (93.2 F), then you would have to take into account that the temperature extremes would fluctuate much more than they do on Earth. A rise to 34 C would effectively wipe out most of life on Earth. Surface water would evaporate, and leave giant inland deserts. Storms would also be so massive, that we currently have no means of classifying them.
It may be possible for a few pockets of life to survive, but the vast majority of the world would be a wasteland. The seas levels would also rise significantly, and low coastal areas would be completely underwater. People could survive there only in underground habitats, or possibly at the poles.
The tropical regions would be completely scorched. Temperatures would exceed 70 C. The ground would be completely dry and parched. The clay would become rock hard, and there would not be any signs of life.
Civilization would be incredibly insular. Since the people would not be able to travel far enough to visit other colonies. The biggest extreme would be people living at opposite poles. Their culture would evolve completely separately from each other, and they would not share a language. The people would also be adapted to the heat.
In conclusion, 34 C is most likely too extreme for humans to prosper. There may be some individuals alive, but there would be a lack of resources, and especially food. It would be far more believable if the temperature was lower. Even 5 C higher on Earth would be pretty extreme.