My car will drop that low which is annoying, considering that I drive an MB with *no power* anywhere below 3000 rpm. I think it's normal, to answer your question, and I don't know if it hurts a diesel to lug it around like that. My solution is to keep my car in third anytime not on the highway. Even locked in third, if I'm traveling at 25 it'll lag or I'll have to kick it down to second in order to really scoot. So I usually just go 50. Everywhere. What can I say - I like throttle response and can't afford a 400/500/AMG anything yet...
I had a 300SD-T a while back and talk about SLOW - I used to drive that car using the gearshift constantly. Probably accelerated tranny death (still got 240k miles out of it though).
In short - I hope a tech answers this, because I've no doubt confused the issue.
Matt (93 190 2.6)