I agree with Sop Monkey. 2 captains on the flight deck = not good in an emergency (non-standard CRM, non-standard relationship between LH and RH seats).
2 captains and a check pilot = potentially disastrous if something goes wrong. All of the above plus "that check guy is watching what we do" and the check guy thinking "I don't want to die; do I trust these two or should I jump in and save it?".
Regarding the Australian A380 was that a well-handled incident? The aeroplane had structural damage, but the the crew spent ages paging through screenfulls of computer fault reports rather than getting on the ground ASAP.