So s that UK 4,54 litres gallon petrol or a US gasoline @ 3.8 something per gal.?
Jet A is 7.01 lbs/ US gallon at 15 Celsius
Elevation of Parchim is 166 feet or 51 meters so I doubt that density altitude played a role, especially with turbo normalized engines.
Not to say there aren't twins that are worse and a few much better.
Any certified twin needs to meet certification requirements so the DA42 is no better or worse then other certified aircraft.
This is not a DA42 airplane issue.
No plane will save you if you are not proficient at what you are doing.
ERA12FA123
ERA09FA303