It varies from subject to subject; there isn't a general 'hard year' or 'easy year' that concerns ALL subjects. For example, Methods was a killer last year, so it will almost certainly be a little easier this year. But Biology was difficult last year, so this year was a little easier. And I find that in general, the 'Arts' subjects (history, the englishes, LOTEs etc.) aren't so badly affected by this whole difficulty issue. It's really mostly the maths/sciences.
I wouldn't worry about difficulty too much - just study hard and go into your exams knowing your stuff. I had to learn this the hard way - worrying too much about difficulty wastes time and gets on your nerves, so it's really not worth it, especially right around exam time!