Probably OK, but use enough heat to stir the water using convection currents.
Alternatively, use a water pump in addition to heat. Go to an aquarist and ask for a miniature aquarium pump (they are about 2 inches long x 1 inch wide x 1 1/2 inches high. This will stir the distilled water more than adequately.
Personally, I find heating the DW to simmering is fully adequate.