My understanding is that the flight was possibly an assessment by CASA on the CP to issue him with check approval for the type within the Rossair training and checking system. This assessment was being conducted concurrently with the assessment of a new pilot to the company or similar.
If that is the case, then I feel that the challenge here is less about the risks associated with multi-engine training and more about the merits of a (technically) unqualified check pilot being assessed by a pilot (from CASA no less) who is not in a control seat, on a pilot who is undergoing a "live" check. "Check-itis" is heavy enough without the added layer of having two check pilots watching on, one who is under real professional pressure...
I've seen this before, and I reckon it can make for a very difficult cockpit environment, regardless of the experience of the personnel involved.
Finally, if the check pilot candidate sets an emergency scenario up incorrectly, who is going to fix it? The candidate undertaking the live check?? Certainly not the guy in the back, he has no flight controls...