The phrase "has been less apparent" is correct and usable in written English.
You can use it when describing a decrease or lack of something. For example, "As technology has advanced, the need for physical paper documents has been less apparent."
What has been less apparent but no less important is the flipside of entry, namely exit.
Mr. Romney's bounce has been less apparent in national tracking polls so far.
Although Titan's surface shows clear evidence of erosional modification, such as fluvial incision, evidence for tectonism has been less apparent.
Central government political support for controversial local decisions has been less apparent.
Similar activity has been less apparent in Europe.
Unfortunately, change has been less apparent in this educational setting, likely due to barriers including heavier teaching responsibilities, resource and financial limitations, and higher representation of students who are at greater risk of failure (Horn and Nevill, 2006; Fischer, 2008; Bueschel and Venezia, 2009; Jaschik, 2009; Keller, 2009).
Since then, the reasons for motivation have been less apparent.
Navarre decided to go ahead with the operation, despite operational difficulties which would later become painfully obvious (but at the time may have been less apparent) because he had been repeatedly assured by his intelligence officers that the operation had very little risk of involvement by a strong enemy force.
As for the governing body: "It was apparent... that regulation by the FA has been less than rigorous".
While we have seen an apparent increase in extreme rightwing violence, there has been less attention paid to it by authorities.
However, early in evolution this would have been less so, and it is apparent that there have continued to exist some populations that experience only weak oxidative stress and that these could maintain a higher diversity of SOD gene sequences.
