To put a little balance on this, and not defending the performance, but flying on the standby A/H is not easy and nor is it regularly practised. Whether or not it was needed as the attitude reference is another matter, but it was 'chosen'. Those of you who have not tried to fly IMC on the stdby A/H with a big AI possibly giving you different attitude information might want to try it in the sim and see how you get on?
If you have an errant main AI a priority is to find a way to cover it. Harking back to the days of the Lightning with its HUGE AI and small standby, you would have seen most pilots had a 'sticky' AI sized patch stuck on their bone-domes, and that was the next item used after control was re-established.
It is not easy!