I've tried it for a few days, in both casual and ranked play (about 9-8) and have concluded that it would only be realistic for farming purposes. In saying that, it simply does not have the intelligence to complete competent moves in order to defeat real humans at a decent level of play. After watching it play with many deck compositions and classes, it just makes too many mistakes that have costed it the game time and time again (i.e, wrong order of card combos etc), while it does make some good plays it's just not enough. After testing on casual for a few days I was able to boost from 40-53 on my warrior for the gold cards aswell as 2-300 gold coins in that period of time with an average win rate of about 45-60% win rate with a control deck. The scummy zoo warlock averaged between 30-45% win rate with varying versions of the deck in order to obtain wider insight into the AI involved.
tl;dr, casual level/ gold coin farming is what hearthbuddy is good at, nothing more