My 05 E320 CDI at 200k mi with Om648 was leaking around the valve cover gasket and was dripping on to the air filter box and exhaust heat shield (engine tilted more towards passenger side) but elsewhere it look pretty dry. I'd be more worried about the injector seal failure (ie black death) than oil leaks.

I bought my E320 CDI for $1900 with a injector seal failure that happened for some time (probally 1-2 yrs) and was daily with that problem, owner never addressed it. I just got done replacing the seals and cleaning, it was quite a job but straightforward (i had worst OM642 oil cooler seal!) and relatively low cost, the kit cost $30 minus the other tools and unforeseen consequences was costly ($200 in tools & custom tools, supplies, broken T return lines $230 OTD)

__________________
Current Garage
2008 Mercedes GL320 CDI 188k mi Repair/Work in progress
1994 S350 160k mi Garage Queen & prepping for repairs
2005 E320 CDI 203k mi Healthy & Daily Driver
1994 S350 357k mi Retried as parts car
1984 300TD 214k mi Blown OM617 Poss OM603 Swap??

Sold
1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi
15+ Others that has come, stay and gone

GONE, BUT NOT FORGOTTEN
1995 E320 SE 220k mi
1984 300SD 350k mi