This is serious issue I must admit and I just cannot assume that you were ignorant of certain things because of your knowledge of mining is enough to implement basic security of your wallet and I am not more skeptical on which wallet is the best one to use if desktop wallet is now vulnerable to this kind of attack. The only explanation to this is the issue of virus which must have created a gateway for the attack to be launched. But I still need to apportion some blame to you that you had to wait for over a month to know something is wrong. It speak more of how much value to place in your assets. Even if you cannot be checking everyday, once in a week won't be too much as you would have been able to take action and the little funds you lost after the main event would have been saved.
Yes you’re right I knew in the back of my mind I should have stored it offline, the reason why I didn’t check my wallet often is because I thought the less I opened it, the safer it would be.