A text I wrote (well, translated actually) contained the phrase:
"the question is highly complex".
After more than a year (!) it's been returned to me with some corrections, and the phrase above has been corrected to "vastly complicated". My first instinct was that this is not right. But I checked on google and found that "vastly complicated" DOES occur but I notice two things about the results:
1) it is attributive i.e. it occurs before the noun rather than as the predicate of the sentence,
2) in all of the finds the word "vastly" seems also to relate to the "vastness" of the noun, not just to the amount of complexity (or complicatedness).
....vastly complicated plot...
....vastly complicated orchestra...
I'm aware that technically complex and complicated also differ in meaning, (complex meaning made of more than one part) but in this particular text I consider that irrelevant. More importantly, complicated has a negative connotation that complex does not. And in my text, the "question" is not treated as negative - indeed it's very interesting and the essayist spends 36 pages answering it.
So my final question is, which would you vote for? The question is highly complex? or The question is vastly complicated?