LHR Rain
I've only heard of 2 failures in total for those transferring direct from left seat B777 to A380. Failure rate amongst F/O's only slightly above the norm. The failure rate for upgrades has historically been higher on the Airbus fleet than those on the Boeing during the actual course but the reverse being true at interview stage. Even so, not what I would call a 'huge' problem but without the actual data in front of me, it would be unwise to fight that statement. From my perspective that is.
Harry