There's also regular chaos with the mis-matched DST windows meaning meetings will swing about by 1-2 hours multiple times as the seasons change depending on whose calendar created them, it's manageable but inevitably there's misses and confusion or someone's 8am suddenly becomes a 6am without rescheduling.
The bigger issue however is if you're the AU leg of a global firm with a US plurality: If there are teams in the UK or EU for example there's simply no way of operating with overlap that doesn't involve someone regularly having meetings in the deeply inhospitable early hours of the morning.