12 months seems normal if stingy in my opinion. Recently I asked in a VW garage about a 2008 car and they wouldn't cover it for 12 months! Just the balance of the manufacturers warranty. From another source I heard the same dealer is struggling. Well no wonder if they've no faith in what they are selling. Some other dealers were only doing 6 months even on car only a couple of years old.
Usually warranties cover the major mechanicals, engine, gearbox etc but might not cover others things like ECU, electrics etc. So you'd have to check the details of specific warranty. Especially if its a car thats known for electrical gremlins etc. I've heard that some dealers don't do the manufacturers used 2yr warranty but do their own 12 month warranty because its more comprehensive.