What kind of guitar are you using with these amps? I've seen people post about diezels missing dynamics only to find out that they had been playing guitars with EMGs :_).
It is true that there is a characteristic compression across all the diezels that I tried (herb, vh3, fokker, hagen) but - they all had one thing in common -> they played really well with low output pickups (teles, strats, LPs with things bridge pups around 8-9kOhm).
This is one of the reasons IMHO why e.g. rectos - which are amps that do not compress and have much more sag - benefit from boosting or using high output pickups. Because they benefit from a narrower compressed tigther signal.
Compared to diezels that benefit from wider and broader and less compressed guitar input sounds.