Yes. - Consider to be and consider as - are both wrong. The correct template idiom is consider X
A. Ezra Pound, considered by some to be one of the foremost poets of the 20th century, was the editor who did most of the editing work on T.S Eliot's Waste Land, a little known fact. ---
consider to be is wrong idiom
B. Ezra Pound, considered one of the foremost poets of the 20th century, was the primary editor of T.S Eliot's Waste Land, a fact not well known by many. ---
The ambiguity of the modifier - a fact not well known by many - is a problem. It should normally modify the noun before, in the case ‘Land’ and it does not stand much logic. Alternatively, it could be that many did not know well that he was he primary editor of T.S Eliot’s wasteland. Alternatively, it could be that he was considered one of the foremost poets was not well known. In any case, the intended meaning is the sufferer. C. It is little known fact that Ezra Pound, considered one of the foremost poets of the 20th century, was the primary editor of T.S Eliot's Waste Land--- straight and clear. Correct choice
D. It is little known that poet Ezra Pound, considered as one of the foremost poets of the 20th century, edited the majority of T.S Eliot's Waste Land. ---
considered as is wrong. In addition the majority is a poor replacement for most
E. Ezra Pound, one of the 20th century's foremost poets, did most of the editing work for T.S Eliot's Waste Land, this is a little known fact. ----
This is a comma splice run-on.