Q:

Can まで be dropped in the XからYまで structure even though the Y is said?

軽く１００人から２００人は超えている

What I think it means: It easily exceeds 100 to 200 persons. 
I have thought about the fact that 超えている could take the place of まで but in this case I think it would be 軽い instead of 軽く...?
More context:

A:

Conjugation of 軽い to 軽く shows that it is meant to be modifying or playing off of a following verb. In this case, that verb would be 超える.
I think that the main difficulty in deciphering this sentence is the fact that they include a 'lowest figure' as well as a 'low figure'. This doesn't appear to be done in most cases using the 軽く超える expression. The reason for this (as far as I can tell) would be done would be to indicate that it is no less than 100 women.
I believe that your translation is correct. Despite proffering a suggestion above as to why the author phrased the sentence as they did, I do not see the source as being a very well-constructed sentence. If it easily exceeds 200, why even mention the 100?
If you use Shonagon, with the search term '軽く超え' (quotes not necessary), 18 results appear. These results only specify one number, which would be considered the 'low figure' (baseline). Following is one of the results:

距離は思ったよりあり、二百メートルは軽く超えてしまった。
The distance was more than expected, easily over 200 meters.

