Pagination (setting the start row), is currently only possible through a url parameter. I see what you are trying to do though... I'll update the BETA to allow you to set a start row in the way you are attempting. However that will break pagination, so you couldn't use that technique in conjunction with next and previous buttons.
I'll get a new BETA out later tonight with the update. I think for now you can get around it by using the SQL statement to set the limit directly like:
$rsFeatures2 = new WA_MySQLi_RS("rsFeatures2",$nMedia3_i,0);
$rsFeatures2->setQuery("SELECT content1.contentID, content1.featureDate, content1.headline, content1.photo1, content1.caption1, content1.para1 FROM content1 ORDER BY content1.featureDate DESC LIMIT 2,4");