There is another possibility, dependant on Crank Case vent pipes.
With most Audi, Mercedes, BMW etc, the perceived turbo oil is not from the Turbo at all.
On a BMW X5 there was a major engine blow-up / runaway diesel issue, the fix upgrade was a centrifugal oil separator to remove oil droplets/mist from the crank case vent prior to venting Crank case fumes to induction.
The Go-faster Audi TT guys tend to fit a Catch-Can set up on the Crank vent between the engine & turbo intake.
I will but money on the likelihood your turbo is fine, & this is where the oil is coming from.
Also note, if this is the case, your intercooler will be 30mm deep in oil & the fins all gunked up too... & all the pipes to/from the intercooler will be oil wet.
The V6 Diesel is a big & high compression engine... and there will be a lot of crank case gasses to clear, even on a good low mileage engine.
a Catch Can is the easy fix.
If you have this much oil in the turbo & pipes, there is a significant risk of an engine runaway...
Scary link below to show you what happens.