Heavy compound exercise like the DL, squat, etc put greater demands on the body. In return producing more engery (combustion) & body heat. Sweating is different in most everyone when working out, including racial groups. Overweight people will tend to sweat the most. Also depends on the workout environment and the clothing one wears. People in good shape will usually take a little longer to work up a good sweat. Normal sweating is healthy and is desired, adnormal sweating is not. What's normal for you may not be for the next guy. Anxities can also cause unusually sweating. If by the 5th rep you are sweating like Old Faithfull that may be just your body type or something else.
If you are having troube catching your breath and sweating a lot, when extra stress is put upon your body through exercise (after a few reps) than something else could be the root cause. May want to check that out with a doctor just to be on the safe side. High blood pressure comes to mind, among other things. A lot of the PL'ers (heavier classes) and BB'ers have raised blood pressure even when not working out.
As for the DL it's self, might try a wider grip or if your gym has a Trap Bar than used that. A Trap Bar gives a more natural position/grip when lifting. Holding the arms, and supporting a heavy weight, in front of the body is not always suited for everyone. Good Luck.
