We purchased tickets at Air Asia's ticket office in Yangon Myanmar for travel to Australia, with a flight change to New Zealand. As UK passport holders, we were not informed we needed visa's to transit thru Sydney Airport to board our Air New Zealand flight. Upon arriving in Kuala Lumpur, Malaysia to catch our connecting flight to Sydney, we were refused boarding and given no assistance by Air Asia. We were stranded in KL for 3 days until we could buy new tickets. To date Air Asia has not replied to a single phone call, email, twitter or message. What is the responsibility of the airline in regards to providing visa information? If the Airline refuses to respond and considering, there are several thousand complaints available on the web about Air Asia's lack of customer service, what is one to do?
No they have no obligation. Visa requirements are highly complicated and depend on many factors, not just which country issued your passport. It is your job as the traveller to understand whatever visa requirements or other restrictions as they apply to you individually.
Incidentally, you did not need a visa if you were arriving on an international flight at Sydney and departing also on an international flight, with less than eight hours in between, under an ordinary UK passport endorsed "British Citizen", and you did not intend to leave the international zone in the airport (for instance to collect bags). If you have a different type of UK passport (such as "British Overseas Citizen" or "British Protected Person") then different restrictions may apply. If your transit actually included domestic travel inside Australia or you needed to recheck your bags, then you could have applied for an evisa (subject to certain requirements) online and this would likely have been approved within a matter of minutes.