All my friends (that I drank my ass off with in college) that went to med school continued to drink hard and advised me that in order to develop cirrhosis you basically need to commit your life to drinking. IE drink whiskey all day every day. Getting hammered 2 nights a week simply won't do it.
It depends on the person, but essentially for most (all?) people it takes decades. Also, abstinence for about a week after a heavy drinking session is enough to full reverse any (known) damage to the liver. But, to be honest, I'd never thought about how much you have to drink across those 10-20 years to get cirrhosis, or whether distribution of drinking has any effect. If I find anything significant I'll post the findings.
But nutritional deficits are rare, even among alcoholics. You have to be going at it pretty hard to the exclusion of everything else for weeks, if not months.
And yeah, there's a lot of drinking going on in our class. Not as much as the Engineers (maybe it's the only way they get laid?

) but it's still a lot. Of course there's the whole spectrum, and I think the rate of abstinence or only light drinking is higher than in most other student groups, but it's still a lot to someone who only has 2-4 drinks most weeks.