Compared to what? Meaning, how do you usually vape that doesn't cause problems?
Guesses:
1) You tense your neck like crazy while trying to build/mount coils?
2) You're getting more efficient vaporization, and have to cut WAY back on the nicotine when using an RDA? (a lot of people vaped 18 mg in a carto, but vape 6 mg in a dripper...)
3) Heat? is the vapor way hotter? Get a longer drip tip, or allow a BUNCH more airflow in the RDA...