I don't see anything wrong with blogging anonymously. I'm one who's doing this. I don't reveal my characters nor where I play publicly. I know there's no big deal because no one knows your real identity behind your characters anyway. It's my choice and if people chose not to read my blog because of that, let it be.
I truely believe if people like your blog, they will read it regardless of knowing who you really are.
Personally this depends on your content. If you are offering raiding advice or PvP advice or some such, being able to show that you have credible knowledge of the topic at hand is/can be an important factor in how people perceive your blog. I can easily write an article talking about how BM is the 2v2 Arena spec of choice and provide lots of theorycraft to back it up but in reality MM is king and anyone with half a brain knows it. Putting a name out there saying "Hey, I have a 2300 rating so I know what I am talking about" goes a long way. The same goes for specific encounter discussions, etc.
And at the same time, a blog focused on more light-hearted aspects (if that is the term I am looking for) may not call for "credibility" per say.