Unless it is a turbocharged aircraft Vmc is a bit academic "at height" as the live one won't be developing anything like 100% power.
Did the instructor/examiner wedge something (their foot for example) under a rudder pedal to simulate loss of rudder authority at "Vmc", or did you actually allow speed to go well below Vmc and therefore close to stall speed - which engine out is fairly exciting.
Yep true. Isn't it called Coffin Corner where Vmc and stall coincide?
It was a Seneca II and so was TC'd (actually develops more HP at altitude than sea level). The examiner didn't wedge his feet under the rudder pedal then, though I believe now they are advised to do so nowadays. I think I would if I were an examiner
I chatted to one FI who lost 5000' in a Vmc demo gone wrong....
Regarding the DA42 - we failed one engine at 5000' in California last year. The weather was reasonably warm, we had lots of fuel (long range tanks) and 3 blokes with overnight baggage onboard. The thing perfomed amazingly and we had no problem climbing at all....(being TC'd helps of course).