Is my Lion Stout infected?

So I got a four pack of Lion Stout, one of my favorite stouts (and beers overall by extension, since stout is The One True Beer) both for the price and in general, and I am really not sure if my memory is bad or if this stuff is really off. I remembered it being really sweet and "roasty" the last time I had it a month or so ago, but this one is very tannic, like I'm drinking a red wine or something. I assumed it was bad but then again I remembered another stout I tried some time ago, can't remember the name but it was an oatmeal stout that had a lot of tannins or whatever and the reviews I read were like "this is so good, lots of tannins, blah blah blah." It wasn't for me but it was also apparently supposed to be like that.

So I guess the question is... obvious tannin/sour taste in a stout, is this automatically a sign of a bad batch, or am I just remembering wrong what it tasted like before?