Tx is and output, the DAT pin of the DHT is an output. It is never good to have 2 outputs connected together. What happens if one is LOW and the other is HIGH? It is called a short circuit. So yes, I think that it could be a problem. Maybe not the problem, but a problem.
After moving that sensor from pin 1, I think that the next thing that I would do is to reduce the wire length and use 10K pullups just to test.
Are you sure that the Pi is capable of supplying sufficient current for the Uno and sensors. The Uno alone needs about 50mA the sensors 1K pullups about 5 mA each + 2mA when each is measuring.