Don,
I pretty much quit using DP series since they went to the DPLF (LF=Lead Free). As I used DP under everything I shot.

Its not as good in my oppinion since it went lead free. The viscosity has gotten thinner your right, plus you have to mix the DT series reducer in it now.
It has a tendency to shrink and soak up the top coat, which it didnt do before.
I dont think it holds up as well either.
I switched to using NCS 2004 sealer thats tintable with DCC toners or DCC color , Lays smooth, and covers well.

Might give that product a try Don.