I've only been getting double gold on the daily battles, not from the daily achievements, skirmishes or pvp. Is that they way its supposed to be?
Yeah. There possibly 4k lost because of two days so they gave you 2k and this which... it depends it could be a lost or gain. So far for me it has been a gain.
Okay, I checked it out and the gold bonus is being rewarded properly. It only applies to the gold earned from the actual match not the bonus gold earned from achievements. Also, all the standard bonus qualifications still apply. As in, if the match is too short or the base match qualification requirements are not met the bonus is not applied. This is to prevent players from abusing the bonus reward system for farming purposes.