The add-on is not required to get the patch, but since they are likely being tested at the same time, the release dates will probably be similar.

You can avoid this bug by not quicksaving.

If you have a legal contract with a publisher stating the terms of the game and patch release process, how exactly do you extrapolate caring? Larian has released unofficial patches for previous games without support or resources from the publisher; if they were able to do so now I'm sure they would. If Larian had even a fraction of Blizzard's resources (even when they started) they would have much more control over publishing.