Another consideration is descent rate. If you are
descending rapidly, the plane won't want to slow down, if
you can achieve high rates of descent with lots of drag,
and hence lower airspeed, you'll still have an increase in
indicated airspeed as you descend into thicker air. This is
most obvious in fighter types where extreme descent rates
will cause Vne to be exceeded due to rapid increase in air
pressure/indicated airspeed. The result, in an extreme case,
could be catastophic structural failure because airframe
stress is proportionate to IAS, not TAS.