Something about the differential DAC scheme has been
bothering me. That is, the IDAC requires a clean virtual-
ground to get proper operation and you have two horns
that both need to sit right. But the job of the op amp
common mode feedback is to keep -outputs- centered
pairwise (keeping Vid=0) but can't control input common
more position.
I suspect that code transitions may result in uncorrected
op amp input deflection, with only input CMRR to fix it,
and that the output CMFB may also (by virtue of being
designed slower than forward amplifier path) contribute
a long low settling time tail.
You might want to look more carefully at amplifier care-
abouts in the application performance-spec context.
Offset errors (w/ dynamic step-to) and settling time in
particular.