It's been a few rough months for Blizzard, their servers have experiences different niggling issues - seemingly since around the release of the latest World of Warcraft expansion, Warlords of Draenor.
Last night, Blizzard's Oceania servers took a tumble with locals reporting on a fan-made Facebook group that "incompatible server" issues being widespread amongst World of Warcraft Oceanic based offerings.
This was confirmed by the Blizzard ANZ Twitter, adding Hearthstone to the list of affected games.
As according to some users, simply closing and re-opening Battle.Net can fix your client for this particular issue and for most of the issues that Blizzard have been experiencing. However sometimes you'll notice that your friends can play the game perfectly fine with no issues whatsoever - this seems to signify that only a section of servers are being affected, not the whole cluster.
Personally, I have had no issues logging in to Barthilas servers in the Oceanic region, but players have been discussing various connection problems as soon as 3 hours prior to the posting of this article.
We will be contacting Blizzard's local PR representative very soon to get the low-down on why their servers have been recently unreliable - stay tuned!