  The low-energy density of states (DOS) of disordered 2D d-wave
superconductors is extremely sensitive to details of both the disorder model
and the electronic band structure. Using diagrammatic methods and numerical
solutions of the Bogoliubov-de Gennes equations, we show that the physical
origin of this sensitivity is the existence of a novel diffusive mode with
momentum close to $(\pi,\pi)$ which is gapless only in systems with a global
nesting symmetry. We find that in generic situations, the DOS vanishes at the
Fermi level. However, proximity to the highly symmetric case may nevertheless
lead to observable non-monotonic behavior of the DOS in the cuprates.
