Both “considered to be” and “considered as” are incorrect. The words “as” or “to be”, when used after the word “considered” are nearly always superfluous, and therefore unnecessary.
The sentence in your example above (without all of the ellipses, of course) is already structured correctly.
Over the past several years, I have noticed both “considered to be” and “considered as” becoming quite commonly used in writing of all types. Although there may be instances where they could possibly be considered correct in a technical sense, both phrases can nearly always be replaced by better wording that makes more, and better, sense. Reading a sentence containing either phrase out loud should be enough to show that these phrases “just don’t sound right”, and tend to disrupt the flow of the words being read.
Although somebody else may consider my answer to your question nitpicking, or even pedantic, I would urge them to consider spending more time reading books that have been copy-edited.
Considering the veritable lack of editing of any kind with regard to “writing”, as encountered on the internet, it would be wise not to consider online media any sort of primer for written communication. This will undoubtedly aid any writer, particularly one who is considerate of the time and energy people may spend viewing his words, in holding the attention of their readers.