My only Wacken so far was 2005 (with Accept headlining the second day...
) and that particular edition of the festival was certainly more balanced amongst the different genres than this year's.
On the two main stages we had a very good mix of genres between classic HM, Thrash, Power, Death, Black, Symphonic and even Doom with Candlemass and Count Raven (they were on the Party Stage). No Folk or Viking (or call it any word you want, you understand what I mean...) on the main stages, but plenty of it on the Party stage with Finntroll, Turisas, Ensiferum and Equilibrium.
If you look at the overall bill, it was not exceptional (2004 was far better). But there was food for everybody's taste.
I've got no knowledge of the difficulties in organizing a big musical event like WOA, so I don't know if this can be the organization's fault, but certainly this year the genres mix is a bit weak.