I drink moderately/socially. My current and previous doctors are aware of my exact habits. Neither ever told me to stop except on Flagyl. Then you absolutely have to. Too much alcohol is never good for anyone. It's true that the meds add work for the liver, but in moderation, I've been told it's fine. If you are very concerned, then of course you should skip the drink.
(I was unable to take Imuran, so I am not as familiar with alcohol interactions, though.)