ADI-2/4 Pro SE and ADI-2 Pro gets warm during operation, that‘s normal.
How much mainly depends on the airflow around the device, not so much on the headphones it drives (aside from some extreme situations).
Typically about 15-30 °C above room temperature.
ADI-2 in balanced mode both headphone amps are combined and active all the time, so it might be some degrees more if driven hard.
When both DAC channels 1/2 and 3/4 are in use, the chips can’t go to idle, which increases power consumption a little.
• Did you estimate, or measure the 50+ °C, and how’s your room?
• Place a thermometer on top to check for the real case temperature.
Looking inside ADI-2 there aren’t too many temperature critical parts inside.
Some PSU caps might benefit from lower temperature, but no such parts in the direct audio path.